.^J# 


IMAGE  EVALUATION 
TEST  TARGET  (MT-3) 


1.0 


I.I 


G£i|28     |25 

Hi  lii    12.2 

£f  144    ■" 


us 

u 


■  40 


12.0 


IL25  III  1.4 


1.6 


-► 


Photographic 

Sciences 

Corporation 


23  WEST  MAIN  STRUT 

WEBSTER,  N.Y.  14580 

(716)872-4503 


\ 


iV 


•s^ 


<x 


oo^^ 


4b 


CIHM/ICMH 

Microfiche 

Series. 


CIHM/iCIVIH 
Collection  do 
microfiches. 


Canadian  Institute  for  Historical  Microreproductions  /  Institut  Canadian  de  microreproductions  historiques 


Taehnical  and  Bibliographic  Notat/Notas  tachniquaa  at  bibliographiquaa 


Tba  inatituta  haa  anamptad  to  obtain  tha  baat 
originai  copy  avaiiabia  for  fiiming.  I^aturaa  of  thia 
copy  which  may  ba  bibliographically  uniqua, 
which  may  altar  any  of  tha  imagaa  in  tha 
raproduction.  or  which  may  aignificantly  changa 
tha  uauai  mathod  of  filming,  ara  chackad  balow. 


0Colourad  eovara/ 
Couvartura  da  couiour 


pn   Covara  damagad/ 


D 


D 


D 
D 


D 


n 


Couvartura  andommagia 


Covara  raatorad  and/or  laminatad/ 
Couvartura  raataurAa  at/ou  palliculAa 


r~n   Covar  titia  miaaing/ 


La  titra  da  couvartura  manqua 


nn   Colourad  mapa/ 


Cartaa  gtegraphiquaa  an  coulaur 


Colourad  ink  (i.a.  othar  than  blua  or  black)/ 
Encra  da  coulaur  (i.a.  autra  qua  blaua  ou  noiral 


|~n   Colourad  plataa  and/or  illuatrationa/ 


Planchaa  at/ou  illuatrationa  wi  coulaur 


Bound  with  othar  matarial/ 
Rail*  avac  d'autraa  documanta 


Tight  binding  may  cauaa  ahadowa  or  dlatortion 
along  intarior  margin/ 

Lareliura  sarria  paut  cauaar  da  I'ombra  ou  da  la 
diatoralon  la  long  da  la  marga  IntAriaura 

Blank  laavaa  addad  during  raatoration  may 
appaar  within  tha  taxt.  Whanavar  poaaibia,  thaaa 
hava  baan  omittad  from  filming/ 
II  sa  paut  qua  cartainaa  pagaa  blanchaa  ajoutiaa 
lora  d'una  raatauration  apparaiasant  dana  la  taxta. 
mala,  loraqua  cala  4tait  poaaibk,  caa  pagaa  n'ont 
paa  Ati  fllmiaa. 

Additional  commanta:/ 
Commantairaa  supplAmantairas: 


L'Inatitut  a  microfilm*  la  maillaur  axamplaira 
qu'il  lui  a  iti  poaaibia  da  sa  procurer.  Las  details 
da  cat  axamplaira  qui  sont  paut-Atra  uniquas  du 
point  da  vua  bibliographiqua,  qui  pauvant  modifier 
una  imaga  raproduita.  ou  qui  pauvant  axiger  una 
modification  dans  la  mithoda  normala  da  fllmaga 
aont  indiquAa  ci-daaaoua. 


□   Colourad  pagaa/ 
Pagaa 


D 


Pagaa  da  coulaur 

Pagaa  damaged/ 
Pagaa  andommagiaa 

Pages  restored  and/oi 

Pages  restauriea  at/ou  pelliculies 

Pagaa  discoloured,  stained  or  foxei 
Pages  dicolories.  tachetAes  ou  piquAes 

Pages  detached/ 
Pages  dAtachias 

Showthroughy 
Transparence 

Quality  of  prir 

Qualiti  inigala  de  I'impression 

Includes  supplementary  matarii 
Comprend  du  matiriel  suppMmentaira 

Only  edition  available/ 
Seule  Mition  disponible 


[~n  Pagaa  damaged/ 

r~1  Pages  reatorad  and/or  laminated/ 

rri  Pagaa  discoloured,  stained  or  foxed/ 

I     I  Pages  detached/ 

I     I  Showthrough/ 

r~1  Quality  of  print  varies/ 

|~~1  Includes  supplementary  material/ 

I — I  Only  edition  available/ 


Pages  wholly  or  partially  obscured  by  errata 
slips,  tissues,  etc.,  hava  been  refilmed  to 
ensure  the  best  possible  image/ 
Lea  pages  totalement  ou  partiailement 
obscurcies  par  un  feuillet  d'errata,  una  pelure. 
etc.,  ont  M  filmAes  A  nouveau  da  fapon  A 
obtenir  la  mailleure  imaga  possible. 


This  item  is  filmed  at  the  reduction  ratio  checked  below/ 

Ce  document  est  film*  au  taux  da  reduction  indiqui  ci-daaaoua. 

10X  14X  18X  22X 


26X 


30X 


J 

12X 


16X 


20X 


24X 


28X 


32X 


Th«  copy  ftlmad  h«r«  hu  b—n  r«produe«d  thanks 
to  th«  gunarotity  of: 

D.B.Waldon  Library 
Univtrtity  of  Wtttcrn  Ontario 
(Regional  History  Room) 

Tho  imago*  appearing  hor*  aro  tho  boat  quality 
poaaibia  conaidaring  tha  condition  and  lagibiiity 
of  tha  original  copy  and  in  Icaaping  with  tha 
filming  contract  spacificationa. 


Original  copioa  in  printad  papor  covora  aro  filmod 
beginning  with  tho  front  covor  and  anding  on 
tho  laat  paga  with  a  printad  or  illuatratad  impraa- 
sion.  or  tho  back  covor  whon  appropriate.  All 
othar  original  copioa  ara  filmed  beginning  on  the 
first  page  with  a  printad  or  illuatratad  impree- 
sion,  ond  ending  on  the  laat  page  with  a  printed 
or  illustrated  impreeaion. 


L'exemplaire  film4  fut  reproduit  grice  i  la 
g4niroait4  do: 

a  B.Wakion  Library 
University  of  Western  Ontario 
(Regional  History  Room) 

Lee  imegea  suhiantee  ont  4t4  reproduitee  avec  to 
plua  grand  soin,  compto  tenu  do  le  condition  et 
do  le  netteti  do  rexemplaire  film*,  et  en 
eonformit*  avec  lea  conditiona  du  contrat  do 
filmege.  ^ 

Lee  exempleiree  origineux  dont  le  couverture  en 
pepier  eet  imprim^o  sent  fllmte  en  commonpant 
par  le  premier  plot  et  en  terminent  solt  per  la 
damlAro  pege  qui  comporte  une  empreinte 
d'impreaaion  ou  d'illustration.  soit  per  le  second 
plot,  selon  le  ces.  Tous  lee  eutres  axempieires 
origineux  sent  fllmte  en  commen9ant  par  la 
pramlAre  pege  qui  comporte  une  empreinte 
dimpreeaion  ou  dlllustratlon  et  en  terminent  per 
la  darniire  page  qui  comporte  une  telle 
empreinte. 


The  leat  recorded  frame  on  eeeh  microfiche 
shell  contain  the  symbol  ^»>  (mooning  "CON- 
TINUED"), or  the  symbol  ▼  (mooning  "END"), 
whichever  epplies. 


Un  des  symbolee  suivanta  apparaltra  sur  la 
domlAro  imege  do  cheque  microfiche,  selon  le 
caa:  le  symbole  — *•  signifie  "A  SUIVRE",  le 
symbole  y  signifie  "FIN". 


Mops,  pletoe,  cherts,  etc.,  mey  be  filmed  at 
different  reduction  retioa.  Thoae  too  lerge  to  be 
entirely  included  in  one  expoeure  are  filmed 
beginning  in  the  upper  left  hend  comer,  left  to 
right  and  top  to  bottom,  ae  many  framea  ae 
required.  The  following  diegrema  illuatrate  the 
method: 


Lee  cartee,  planches,  tableeux,  etc..  peuvent  Atre 
fllm4e  i  doe  taux  da  rMuction  diffirants. 
Lorsque  le  document  est  trop  grond  pour  Atre 
reproduit  en  un  soul  clich4,  il  est  film*  it  partir 
da  Tangle  supAriour  geuche,  do  geuche  *  droite, 
et  do  heut  en  bee.  en  prenent  le  nombre 
d'Imeges  n*cessaire.  Lea  diagrammes  suivanta 
illuatrent  le  m*thode. 


1 

2 

3 

1 

2 

3 

4 

5 

6 

RESEARCHES 


ON  TU 


DOUBLE  HALIDES. 


A  DISSERTATION 


PMWiTBD  TO  THB  SOAKD  OF  UNIVBMrrT  STimUS  OT  THB  JOHNfr  MnCIMS 

UNivnsrry  vok  thb  diguui  or  ixjctob  ov  renoaoPHT 


BY 


CHARLES  E.  SAUNDERS. 


1801. 


BALTIMORE: 

Pfttn  OP  Isaac  Friedbnwald  Co. 

1891. 


RESEARCHES 


ON  THE 


DOUBLE  HALIDES 


A  DISSERTATION 


PRESENTED  TO  THE  BOARD  OF  UNIVERSITY  STUDIES   OF   THE    JOHNS    HOPKINS 
UNIVERSITY  FOR  THE  DEGREE  OF  DOCTOR  OF  PHILOSOPHY 


BY 


CHARLES  E.  SAUNDERS. 


1891. 


BALTIMORE : 

Press  of  Isaac  Friedenwald  Co. 

1891. 


Ini 
Pa 


Pad 


The 
Bio( 


'«(• 

h 


CONTENTS. 

rAOB 

Introduction i 

Part  I.    Manqanesb  Compounds 2 

Manganout  Chloride a 

Experimentt  with  Potassiam  Chloride 4 

Experiments  with  Ammonium  Chloride 9 

Experiments  with  Rubidium  Chloride 14 

Experiments  with  Ciesium  Chloride 18 

Experiments  with  Magnesium  Chloride 23 

Negative  Results 25 

Conclusion 26 

Part  II.    Antimony  Compounds 27 

Experiments  with  Casium  Chloride 27 

Experiments  with  Rubidium  Chloride 30 

Summary 38 

Theoretical 38 

Biographical  Sketch 40 


The  present  investigation  was  carried  out  under  the  direct 
supervision  of  Prof.  Ira  Remsen,  to  whom  the  author  wishes  to 
express  his  sincere  gratitude  for  the  instruction  received. 

The  writer  would  also  express  his  thanks  to  Dr.  G.  H.  Williams 
for  assistance  in  the  crystallographic  part  of  the  work. 


INTRODUCTION. 


The  investigation,  an  account  of  which  is  here  given,  bears  on 
the  general  questions  as  to  the  structure  and  the  conditions  of 
formation  of  the  double  halides.  Compounds  of  this  class,  though 
known  for  many  years,  did  not,  until  recently,  attract  much 
attention.  Being  regarded  as  molecular  and  not  atomic  com- 
pounds, the  investigation  of  their  structure  seemed  to  present 
unusual  difficulties.  The  apparent  analogies  between  the  double 
halides  and  the  oxygen  salts  were  frequently  discussed,'  but  it  was 
not  until  1867  that  the  conception  of  the  union  of  the  molecules 
through  the  chlorine  atoms  was  first  put  forward  by  Naquet.* 
This  theory  has  since  been  expressed  by  several  other  chemists,* 
and  was  recently  fully  discussed  by  Professor  Remsen,*  who  laid 
special  stress  on  the  view  that  pairs  of  halogen  atoms  exert  a  link- 
ing function  in  these  compounds  similar  to  that  exerted  by  single 
oxygen  atoms  in  the  oxygen  salts,  and  formulated  the  following 
law  in  regard  to  the  composition  of  the  double  halides : 

"  When  a  halide  of  any  element  combines  with  a  halide  of  an 
alkali  metal  to  form  a  double  salt,  the  number  of  molecules  of  the 
alkali  salt  which  are  added  to  one  molecule  of  the  other  halide  is 
never  greater  and  is  {generally  less  than  the  number  of  halogen 
atoms  contained  in  the  latter." 

This  law  was  based  on  the  formubn  of  several  hundred  double 
halides ;  nevertheless,  a  few  exceptions  to  it  are  found  recorded 
in  chemical  literature.  Some  of  these  records  have  already  been 
shown  to  be  incorrect. 

The  present  paper  treats  in  the  first  part  of  some  of  the  double 
halides  containing  manganese,  and  in  the  second  chiefly  of  some 
of  the  supposed  exceptions  to  the  law  stated  above. 

>Von  Bonidorff,  Ann.  chim.  phys.   [a]  34,  14a:   Boullay,  Ibid,  [a]  34,  337;   Boltey, 
Liebig's  Ann.  89, 100 ;  Liebig,  Ann.  chim.  phys.  [a J  35,  68;  Berzelius,  Ben.  Jahrsb.  8,  138. 

>  Principes  de  Chimie  fondle  lurles  Theories  Modernes,  Paris,  1867,  p.  6a. 

>  See  especially  Blomttrand,  Die  Chemie  der  Jetztzeit  etc.,  Heidelberg,  1869 ;  Armstrong, 
British  Assoc.  Reports,  1885,  939;  Heyes,  Phil.  Mag.  38,aat,  a97. 

*  Am.  Chem.  Jour.  11,  391. 


Part  I. 

Manganese  Compounds. 

The  followinK  is  a  list  of  the  salts  hitherto  described  containing 
manganous  chloride,  combined  with  the  chloride  of  some  alkali 
metal  (or  of  ammonium): 

NH«MnClt.aHiO 
(NH«)iMnCl«.HtO 
(NHOiMnCUaHiO 
RbiMnCh 
RbtMnCl«.3HiO 
CsiMnCh 
CsiMnCU.sHiO 
a(Cs«MnC10.5HaO. 
Each  of  the  salts  in  this  very  irregular  series  will  be  considered 
in  detail  in  its  proper  connection.    There  is,  however,  a  salt  which 
should  be  considered  before  taking  up  the  compounds  in  this  list 
and  those  closely  related  to  them. 


Manganous  Chloride,  MnCUaHiO. 

In  attempting  to  prepare  a  double  chloride  of  manganese  and 
lithium,  and  also  of  manganese  and  magnesium,  a  substance  was 
obtained  which  proved  to  be  manganous  chloride  with  two  mole- 
cules of  water  of  crystallisation  instead  of  four,  which  is  the  normal 
number.  The  new  form  of  the  substance  was  obtained  by  adding 
a  considerable  quantity  of  ordinary  manganous  chloride  to  a 
concentrated  solution  of  lithium  chloride  in  water,  then  evapor- 
ating somewhat  and  allowing  to  cool.  When  magnesium  chloride 
was  used  instead  of  lithium  chloride,  either  alcohol  containing 
water,  or  water  alone  served  as  the  solvent,  a  few  drops  of  hydro- 
chloric acid  being  usually  added.  When  magnesium  chloride  is 
present  there  must  be  added  a  considerable  excess  of  manganous 
chloride,  or  a  double  salt  will  be  produced  instead  of  the  simple 
chloride.  Manganous  chloride,  as  thus  obtained,  crystallised  in 
beautiful  pink  crystals,  usually  about  one  centimeter  in  length  and 
quite  slender.  The  ends  of  the  crystals  were  frequently  hollow  for 
some  distance  inward.  They  usually  formed  radiating  groups, 
but  were  sometimes  obtained  in  perfectly  definite  crossed  twinp. 


I 


inese  and 
tance  was 
wo  mole- 
le  normal 
}y  adding 
•ide  to  a 
n  evapor- 
chloride 
ontaining 
ofhydro- 
ihloride  is 
anganous 
e  simple 
allised  in 
ngth  and 
ollow  for 
groups, 
sed  twins. 


The  substance  acts  in  general  like  ordinary  manganous  chloride, 
except  that,  as  would  be  expected,  it  does  not  lose  water  of  crys- 
tallisation when  dried  over  calcium  chloride,  while  the  ordinary 
form  loses  two  of  its  four  molecules  under  these  conditions. 
Analysis  showed  that  the  same  salt  was  obtained  from  a  solution 
containing  lithium  chloride  as  from  one  containing  magnesium 
chloride.  From  the  conditions  of  formation  a  pure  product  could 
not,  however,  be  expected.  The  analyses  here  given  were  made 
first  with  a  sample  which  had  been  dried  between  filtering  paper, 
and,  second,  with  one  dried  to  constant  weight  over  calcium 
chloride. 

Analysis  of  salt  dried  between  filtering  paper  gave  the  following 
results : 

0-3924  gram  salt  gave  0.6753  gram  AgCl  (42.56  per  cent.  CI), 
and  0.1788  gram  Mni04  (32.82  per  cent.  Mn). 

When  dried  over  calcium  chloride  the  salt  gave  the  following 
figures  on  analysis : 

0'3346  gram  salt  gave  0.5902  gram  AgCl  (43.62  per  cent.  CI), 
and  0.1 58 1  gram  MniiO«  (34.03  per  cent.  Mn). 

0-2975  gram  lost  at  los'-i  10"  0.0326  gram  H«0  =  10.96  per 
cent.  HtO. 

At  higher  temperatures  further,  but  slow,  loss  was  observed, 
no  doubt  due  to  decomposition  of  the  salt. 

Calculated  FovRll 


for  MnCI, 

.aH,0. 

In  dried  lalt. 

In  undriad  lalt. 

Mn 

54-8 

33-94 

34-03 

32.82 

2CI 

70.74 

43.81 

43.62 

42.56 

H.O 

17.96 

11.125 

10.96 

H.O 

17.96 
16T.46 

11.125 
100.000 

m    y       It  is  evident,  therefore,  that  the  salt  has  the  formula 
MnClt.2HiO,  and  loses  one  molecule  of  water  at  105**. 
Crystallography  of  the  salt. — It  crystallises  in  slen- 
der prisms  (Fig.  i),  which  were  shown  by  their  optical 
properties  and  angular  measurements  to  be  monoclinic. 
The  crystals  were  usually  hollow  towards  the  end,  so 
Fig.  I.      that  the  basal  plane  was  very  imperfectly  developed. 
On  this  account  the  crystallographic  angle  /?  was  found  (roughly) 
by  measurement  on  a  petrographical  microscope,  the  crystal 


resting  on  one  of  the  clinopinacoids.     The  other  angle  was 
measured  on  a  Fuess  goniometer.    The  forms  observed  were : 

c  =:  oP,  [ooi]. 
»*=ooP,  [no]. 
^^  00  Poo,  [oio]. 

The  angles  measured  were  \  'm\m:=.  ioo°  45',  and  Z/5^42'' 

(nearly).    From  these  data,  taking  T>  as  unity,  we  have  d.  =  1.238 

(nearly). 
The  substance  sometimes  forms  crossed  twins  in  which  the 

basal  plane  is  the  twinning  plane.    An  orthographic  projection  of 

such  a  twin  is  shown  in  Fig.  2. 

It  seems  probable  that  the  magnesium 
chloride,  or  lithium  chloride,  present 
when  manganous  chloride  crystallises 
out  with  only  two  molecules  of  water 
must  act  as  a  sort  of  dehydrating  agent; 
and  it  is  not  unlikely  that  the  presence 
of  such  salts  as  these  in  solutions  in 
other  cases  would  lead  to  the  formation 

of  crystals  of  various  substances,  containing  less  than  their  normal 

number  of  molecules  of  water. 


Fig.  2. 


Experiments  with  Potassium  Chloride,  e*c. 

On  adding  potassium  chloride  to  a  hot  aqueous  solution  of 
manganous  chloride,  sufficiently  concentrated  to  deposit  crystals 
on  cooling,  a  considerable  amount  of  the  alkali  chloride  is  dis- 
solved. When  the  solution  cools  crystals  of  a  double  chloride 
are  deposited,  which  are  pale  pink  in  color,  and  usually  form 
radiating  groups.  The  individual  crystals  are  elongated  and  very 
thin  as  produced  in  this  way ;  but  by  spontaneous  evaporation  of 
the  solution  they  can  be  obtained  in  much  larger  form.  They  are 
very  soluble  in  water,  but  cannot  be  recrystallised  in  the  ordinary 
sense  of  the  term,  for  their  solution  gives  a  deposit  of  potassium 
chloride  only,  until  the  manganous  chloride  is  present  in  large 
excess.  This  decomposition  of  the  salt  occurs  in  the  same  way 
in  the  presence  of  hydrochloric  acid,  and  seems  to  depend  merely 
on  the  different  solubilities  of  the  two  constituents. 

The  salt  is  deliquescent  in  moist  air,  and  was  therefore  dried  in 
a  desiccator  over  calcium  chloride  before  analysing.    It  seems  to 


I  was 
e: 


=  42° 
1.238 

:h  the 
tion  of 

nesium 

present 

itallises 

water 

agent; 

resence 

ions  in 

rmation 

normal 


ition  of 
crystals 
is  dis- 
:hloride 
lly  form 
|nd  very 
Ration  of 
'hey  are 
trdinary 
>tassium 
^n  large 
ime  way 
merely 

iried  in 
keems  to 


retain  its  water  of  crystallisation  under  these  conditions,  though 
a  slow  loss  in  weight  continues,  probably  due  to  the  giving  up  of 
two  molecules  of  water  of  crystallisation  by  the  manganous 
chloride  mechanically  mixed  with  the  salt.  The  presence  of  this 
manganous  chloride  accounts  for  the  lack  of  agreement  between  the 
percentage  composition  found  and  that  calculated.  As  manganous 
chloride  retains  one  molecule  of  water  at  110°,  the  analysis  of  the 
salt  could  not  be  expected  to  give  figures  adding  up  quite  to  100 
per  cent. 

The  method  used  for  the  determination  of  the  potassium  and 
manganese  was  as  follows  :  The  manganese  was  precipitated  as 
carbonate  by  means  of  ammonium  carbonate  and  then  burned  to 
mangano-manganic  oxide,  while  the  filtrate  was  evaporated  and 
the  potassium  weighed  as  chloride,  after  subliming  off  the  ammo- 
nium chloride.  The  same  method  was  used  in  the  case  of  the 
rubidium  and  caesium  salts.  Here  it  has  the  great  advantage  of 
giving  the  alkali  metal  back  again  in  the  desired  form.  Th .  pre- 
cipitation of  manganese  by  ammonium  carbonate  was  found  to  be 
almost  absolutely  complete.  Where  the  filtrate  containing  the 
alkali  chloride  was  evaporated  in  glass  vessels,  a  blank  experi- 
ment, performed  under  similar  conditions,  gave  the  amount  of 
glass  dissolved,  which  was  then  deducted. 

0.4562  gram  salt  gave  0.1479  gram  Mn804  (23.35  P^""  cent. 
Mn),  and  0.1415  gram  KCl  (16.27  per  cent.  K). 

0.2969  gram  salt  gave  0.5388  gram  AgCl  (44.88  per  cent.  CI). 

0.2517  gram  salt  lost  at  los"-!  10®  0.0381  gram  HiO=  15.14 
per  cent.  HaO. 

Calculated.  Found. 

39.03  16.55  16.27 

106. 1 1  44.99  44.88 

54.8  23.23  23.35 

35-92  15.23  15.14 


K 

3CI 

Mn 
2H.O 


235.86  100.00  99-64 

The  salt  has  therefore  the  formula  KMnCl«.2H20.  It  has  not 
been  previously  described.  All  efforts  to  obtain  a  salt  containing 
a  larger  proportion  of  potassium  chloride  failed.  No  iodide  or 
fluoride  of  manganese  and  potassium  was  obtained,  nor  was  a 
bromide  obtained  by  itself,  though  the  substance  described  below 
may  be  regarded  as  containing  a  simple  double  bromide. 


6 


Efforts  were  made  to  produce,  if  possible,  mixed  salts  (a  chlor- 
bromide  and  a  chlor-iodide)  of  definite  composition.  These 
experiments  will  now  be  described. 

If  a  hot,  saturated  solution  of  manganous  chloride  be  saturated 
with  potassium  bromide  and  then  allowed  to  cool,  crystals  are 
deposited  exactly  similar  in  appearance  to  those  of  the  salt 
KMnCls.2H30,  but  containing  a  considerable  amount  of  bromine. 
On  evaporation  of  the  solution  further  deposits  of  crystals  can  be 
obtained.  The  percentage  of  bromine  was  found  to  vary  in 
different  crystallisations,  as  shown  by  the  following  analyses,  the 
first  being  of  a  very  early  deposit  and  the  second  of  a  much  later 
one: 

I.  0.7380  gram  of  the  salt  was  dissolved  in  500  cc.  of  water  and 
divided  into  two  equal  parts.  In  each  portion  the  chlorine  was 
precipitated  as  silver  chloride,  one  of  the  precipitates  being  col- 
lected and  weighed  in  a  Gooch  crucible,  while  the  other  was 
reduced  to  metallic  silver  in  a  current  of  hydrogen. 

0,3690  gram  gave  0.6621  gram  AgCl  +  AgBr,  and  0.4823 
gram  Ag.  Hence  Br  =  0.03836  gram  =  10.40  per  cent.,  and 
CI  =  0.14144  gram  =  38.33  per  cent. 

II.  The  amount  of  silver  which  a  given  weight  of  the  salt  would 
precipitate  was  determined  volumetrically  (by  Mohr's  method), 
and,  in  a  separate  portion,  the  weight  of  the  mixed  precipitates 
formed  from  a  given  amount  of  the  salt  was  determined.  This 
method  is  more  rapid  than  the  one  previously  mentioned,  but  the 
results  are  probably  less  accurate. 

0.3134  gram  salt  gave  0.5434  gram  AgCl  -\-  AgBr,  and  0.3238 
gram  precipitated  0.40001  gram  Ag.  Hence  Br  =  0.0521  gram 
in  0.3134  gram  salt  =16.62  per  cent,  and  0=0.1041  gram  in 
0.3134  gram  salt  =:  33.22  per  cent. 

III.  A  complete  analysis  was  made  of  a  deposit  intermediate 
between  the  two  just  given. 

0.4719  gram  lost  at  105"-!  10*  0.0671  gram  HsOzr  14.22  per 
cent.  H2O,  and  gave  0.1564  gram  KsS04  (14.88  per  cent.  K),  and 
0.1395  gram  MmOi  (21.29  per  cent.  Mn). 

0.3426  gram  gave  0.5966  gram  AgBr  -|-  AgCl,  and  0.3133  gram 
precipitated  0.3916  gram  Ag.  Hence  Br=:  14.53  per  cent.,  and 
CI  =:  34.62  per  cent.  In  this  case  the  potassium  was  weighed  as 
sulphate,  to  ensure  the  absence  of  bromine. 


irated 
Is  are 
e  salt 
Dmine. 
can  be 
ary  in 
es,  the 
;h  later 


|d  0.3238 

i2i  gram 

gram  in 

Irmediate 

I14.22  per 
K),  and 

|i33  gram 
cent.,  and 
leiglied  as 


The  above  analyses  show  that  the  substance  obtained  is  not  a 
definite  compound,  but,  in  all  probability,  an  isomorphous  mix- 
ture of  two  salts.  It  was  found  by  calculation  that  the  mixture 
might  consist  of  77.2  per  cent.  KMnCli.2H»0  with  22.8  per  cent. 
KMnBri.2HiO,  or,  supposing  the  mixed  salts  to  exist,  of  48.05 
per  cent.  KMnCl8.2H«0  with  51.95  per  cent.  KMnCl»Br.2HsO. 


Calculated  for  both  mixtures. 

Found. 

CI 

34-73 

34.62 

Br 

14.78 

14.53 

Mn 

21.32 

21.29 

K 

15.19 

14.88 

H»0 

13.98 

14.22 

100.00 


99.54 


As  the  substance  comes  out  of  a  solution  containing  a  large 
excess  of  manganous  chloride,  as  well  as  some  manganous  bro- 
mide, the  agreement  between  the  calculated  composition  and  that 
found  can  hardly  be  expected  to  be  very  close.  The  fact  that  the 
salt  KMn6rs.2H90  was  not  obtained  in  the  experiments  with  the 
pure  bromides  might  be  considered  as  an  argument  in  favor  of 
the  belief  that  the  constituent  containing  bromine  in  this  mixture 
was  really  some  mtxedsa.lt,  such  as  KMnCl!iBr.2HsO.  However, 
the  explanation  that  the  presence  of  the  salt  KMnCl».2HaO  gives 
crystallising  power  to  the  salt  KMnBr8.2H30,  so  that  the  two  can 
form  an  isomorphous  mixture,  involves  perhaps  less  speculation. 

When  potassium  iodide  was  used  instead  of  the  bromide,  in 
attempting  to  prepare  a  mixed  salt,  crystals  of  the  same  habit  as 
before  were  obtained.  A  complete  analysis  of  these  was  made, 
and  the  salt  was  found  to  contain  an  amount  of  iodine  so  small 
that  it  must  be  considered  as  a  non-essential  constituent,  present 
merely  by  the  adhering  of  a  certain  amount  of  mother-liquor. 
The  salt  is  too  easily  soluble  to  admit  of  its  being  washed  to  any 
considerable  extent.  In  no  case  was  so  much  as  i  per  cent,  of 
iodine  found.     The  salt  was,  in  fact,  KMnCl3.2HsO. 

These  experiments  are  of  interest  as  showing  what  large 
amounts  of  potassium  bromide  and  iodide  are  converted  into  the 
chloride  by  being  dissolved  in  a  solution  of  manganous  chloride. 
These  crystallisations  were  all  made  in  neutral  solutions  so  as  to 
avoid  the  complications,  in  interpreting  the  results,  which  the 
presence  of  even  a  small  quantity  of  acid  would  have  introduced. 


8 


II I 


On  adding  excess  of  potassium  chloride  to  a  warm,  saturated 
solution  of  manganous  bromide  in  water,  filtering  while  hot,  and 
allowing  to  cool,  a  deposit  of  crystals  was  obtained  consisting 
largely  of  potassium  bromide.  The  solution  was  then  evaporated 
and  each  successive  deposit  of  crystals  removed  until  a  point  was 
at  length  reached  where  crystals  similar  to  those  of  KMnCli.2HiO 
were  formed.  They  contained  bromine  and  manganese,  as  well 
as  potassium  and  chlorine.  Analysis  showed  that  they  did  not 
correspond  in  composition  to  any  definite  simple  salt,  but  were  a 
mixture  (probably  an  isomorphous  mixture)  of  two  or  more  com- 
pounds. It  is  probable  that  this  substance  contained  the  same 
salts  as  that  produced  by  adding  potassium  bromide  to  a  solution 
of  manganous  chloride. 

A  similar  experiment  using  manganous  iodide  instead  of  the 
bromide  gave  no  satisfactory  results,  manganous  iodide  being 
rather  too  unstable  for  this  work.  It  was  not  to  be  expected, 
however,  that  a  double  salt  would  be  obtained  in  this  experiment, 
because  the  composition  of  the  salts  already  described  seems  to 
prove  that  both  manganous  chloride  and  potassium  chloride  are 
necessary  constituents  in  every  case.  The  experiments  with  man- 
ganous chloride  and  potassium  iodide  showed  how  readily  the 
chlorine  passed  over  from  the  manganese  to  the  potassium,  so 
that  it  does  not  seem  probable  that  the  reverse  action  would  take 
place  to  any  considerable  extent ;  hence  the  solution,  in  the  expe- 
riment just  mentioned,  would  contain  only  a  very  small  quantity 
of  manganous  chloride,  and  the  formation  of  a  double  salt  would 
not  be  possible. 

Crystallography  of  the  salt. — Accurate  measurements  of  the 
crystals  were  found  very  difficult,  owing  to  the  softness  of  the  salt 
and  its  tendency  towards  deliquescence.  Sufficient 
information  was  obtained,  however,  from  the  optical 
properties  and  measurements  of  some  angles  to  show 
that  the  crystals  are  triclinic.  Individual  crystals 
often  show  very  irregular  development.  The  draw- 
ing given  (Fig.  3)  is  merely  to  show  their  general 
shape,  as  most  commonly  obtained,  h.%  gliding 
is  very  readily  produced  in  this  salt,  a  sample  of  it 
was  sent  to  Prof.  Otto  Miigge,  of  the  University 
of  Milnster,  who  has  been  for  some  time  making  a 
special  study  of  that  phenomenon.  He  has  kindly 
Fig.  3.         undertaken  an  investigation  of  the  compound. 


rv 


9 


Experiments  with  Ammoriutn  Chloride. 

Up  to  the  present  time  there  have  been  described  three  com- 
pounds of  manganous  chloride  with  ammonium  chloride : 

NH4MnCk2H«0,  described  by  Hautz,' 

(NH4)aMnCl4.HsO,  described  by  Rammelsberg'and  by  Pickering,' 

(NH4)»MnCl4.2HiO,  described  by  v.  Hauer.* 

The  directions  given  by  Hautz  for  the  preparation  of  the  salt 
described  by  him  are  simple.  A  solution  of  manganous  chloride 
and  ammonium  chloride,  mixed  in  the  proportions  required  by 
the  formula  NHiMnCh,  is  to  be  evaporated  to  crystallisation. 
These  directions  being  followed,  a  salt  was  obtained,  which  was 
evidently  the  same  as  that  described  by  Hautz.  Analysis  proved, 
however,  that  its  formula  was  not  NH<MnCl8.2H30,  but 
(NH4)4MnCl4.2HiO,  though  the  salt  as  thus  produced  was  not 
very  pure.  A  pure  product  was  afterwards  obtained  by  mixing 
the  two  chlorides  in  about  the  proportions  mentioned  by  Hautz, 
and  allowing  the  aqueous  solution  to  evaporate  spontaneously  for 
several  months  over  sulphuric  acid.  At  intervals  the  deposits  of 
crystals  were  removed.  The  fifth  sample  was  found  to  be  pure ; 
the  others  contained  an  excess  of  ammonium  chloride. 

The  analyses  of  the  salt  gave  the  following  results : 

0.3693  gram  gave  0.7870  gram  AgCl  (52.70  per  cent.  CI). 

0.3557  gram  gave  0.1008  gram  Mn804  (20.41  per  cent.  Mn). 

1. 1389  gram  lost  at  110*0.1529  gram  HsO=:  13.43  percent. 
H.O. 

0.3015  gram  gave  0.04037  gram  NHi^  I3«39  per  cent.  NH4. 

The  determination  of  the  water  of  crystallisation  in  this  salt  is 
of  no  value.  The  water  is  not  given  off  readily,  and  the  anhy- 
drous salt  undergoes  slow  decomposition  at  i  lo**.  The  figures 
given  merely  indicate,  therefore,  the  point  beyond  which  the  loss 
of  weight  was  very  slow. 

Calculated  for  (NH4)aMnCl4.aHjO.  Found. 

Mn  54.8  20.43  20.41 

4CI  141.48  52.75  52.70 

2NH4  36.02  13.43  13-39 

2H>0  35-92  13.39  13-43 


268.22 

■  Liebig's  Annalen  06,  285. 
•Jour.  Chem.  Sec,  1879,  654. 


100.00 


99-93 


'  Pogg.  Ann.  94,  507. 

4  Jour.  fuT  pr.  Chem.  63, 436. 


10 


'  il 


il 


1 


The  salt  usually  forms  radiating  groups  of  short  crystals.  It  is 
pale  pink  in  color  and  of  hard  texture.  It  is  easily  soluble  in 
water,  but  cannot  be  obtained  very  pure  by  recrystallisation,  as  it 
requires  the  presence  of  an  excess  of  manganous  chloride  before 
it  crystallises  in  quite  pure  condition.  It  is  not  deliquescent  in 
the  air,  and  does  not  give  up  its  water  of  crystallisation  in  a 
desiccator. 

Crystallography  of  the  salt. — Well-developed,  individual  crys- 
tals are  not  often  obtained,  and  when  found,  the  faces  are  not,  as  a 

rule,  bright  enough  for  a  satisfactory 
measurement  of  the  angles  with  a  gonio- 
meter. The  salt  (Fig.  4)  is  monoclinic  in 
crystallisation,  but  possesses  certain  pecu- 
liarities due  to  the  fact  that  two  of  its  axes 
are  almost  (if  not  exactly)  equal  in  length. 
While  the  values  obtained  for  these  axes 
are  not  identical,  the  difference  is  quite 
within  the  possible  error  caused  by  the 
^'°'^"  imperfections  of  the  crystal  faces.    Owing 

to  the  habit  of  the  crystals  and  the  similarity  in  length  of  two  of 
the  axes,  there  is  some  resemblance  between  crystals  of  this  salt 
and  a  rhombic  dodecahedron.  The  cleavage  is  imperfect.  The 
optical  properties  show  that  the  crystals  are  monoclinic.  The 
position  off  the  b  axis  (the  axis  of  symmetry)  was  determined  by 
the  extinction  phenomena  of  the  substance. 
The  forms  observed  were  oP,  00  P  53,  -f-  P  and  —  P. 


Measurements  obuined. 

Angles  calculated. 

Ill :  Tii  =  121*  36J' 

121**  37' 

III :  III  =   90"  16}' 

90"  17' 

III :  Iii^   95"  42' 

95"  42' 

III :  100::=  121**  30' 

121"  29J' 

III :  iiT=  121°  36}' 

121*  48' 

HI  :  100=  117**  43' 

116°  53i' 

001 :  100=   95"  25' 

95"  25' 

III :ooi 

121"  26i' 

III :ooi 

ii6«47i' 

These  measurements  were  all  made  (except  the  last)  from  one 
crystal  of  the  pure  salt  as  used  for  analysis.  The  first  four  meas- 
urements were  believed  to  be  the  best,  and  were  therefore  used  in 


11 

calculating  the  lengths  of  the  axes,  and  the  angle  /9.  They  are 
probably  correct  within  5'  or  6'.  Those  lower  on  the  list  were  not 
believed  to  be  as  good.    The  constants  found  were : 

^^1.4913  ^=1 

^  =  1.4956  Z/S  =  84«'35' 

Hautz  describes  the  salt  obtained  by  him  as  crystallising  in  the 
nionoclinic  system.  The  symbols  he  gives  for  the  forms  observed 
appear  to  mean  that  the  crystals  consisted  of  a  prism,  ortho  and 
clino  domes,  with  perhaps  one  of  the  pinacoids  poorly  developed. 
The  symbol  of  the  latter  is  enclosed  in  a  parenthesis,  and  it  is 
not  clear  to  which  pinacoid  it  refers.  Now,  by  placing  the  crys- 
tals obtained  in  this  investigation  in  an  incorrect  position  the 
forms  would  become  the  same  as  those  given  by  Hautz,  except 
that  no  plane  corresponding  to  his  undetermined  pinacoid  was 
observed.  The  evidence  is  therefore  pretty  clear  that  the  two 
salts  are  identical.  The  analyses  of  Hautz  show  that  the  sub- 
stance as  obtained  by  him  was  very  impure,  whatever  its  formula 
may  have  been.  He  describes  the  salt  as  losing  li  molecules  of 
water  at  100*,  and  the  remainder  at  135°.  It  has  already  been 
pointed  out  that  determinations  of  the  water  in  this  salt  are  quite 
unreliable  on  account  of  the  tendency  to  decomposition  and  the 
difficulty  with  which  the  water  is  driven  off  at  about  1 10".  The 
figures  given  by  Hautz  are  as  follows : 


For  salt  undried. 

For  salt  dried 

at  100°. 

Calculated. 

Found. 

Calculated. 

Found. 

NH« 

8.32 

8.2 

9.84 

•  •• 

Mn 

25.90 

•  •  • 

29-54 

28.69 

CI 

49.12 

«  •  • 

55.76 

55-52 

H,0 

16.66 

17.4 

4.86 

4.09 

100.00 


100.00 


These  figures  would  be  somewhat  different  if  calculated  on  the 
basis  of  the  atomic  weights  now  in  use ;  but  even  then  the  lack  of 
agreement  between  the  numbers  calculated  and  those  found  by 
analysis  would  be  too  great,  in  some  cases,  to  be  attributed  to 
errors  of  experiment.  From  these  partial  analyses  Hautz  derives 
the  formula  (using  our  present  atomic  weights)  NH4MnCli.2HaO 
for  the  undried  salt,  and  NH«MnCU.}HiO  for  the  salt  dried  at  100°. 

It  was  not  found  possible  to  prepare  this  substance.    Even 


12 


vm' 


i 


' 


when  a  large  excess  of  manganous  chloride  was  present  the  salt 
(NH«)aMnCl4.2HiO  was  invariably  obtained.  From  a  considera- 
tion of  all  the  evidence,  the  conclusion  is  drawn  that  the  salt 
obtained  by  Hautz  was  really  (NH4)«MnCl4.2HiO  in  an  impure 
condition,  and  that  no  salt  exists  having  the  formula  NHiMnCli. 
2H9O.  This  conclusion  was  quite  unexpected,  as  it  was  naturally 
supposed  that  there  would  be  an  ammonium  salt  corresponding 
to  the  potassium  salt  obtained.  The  relations  between  all  the 
members  of  this  series  of  salts  will  be  referred  to  farther  on. 

The  salt  (NH0>MnCl4.2H9O,  as  obtained  and  analysed  by 
V.  Hauer,  seems  to  have  been  quite  impure.  He  describes  it  as 
crystallising  in  cubes  of  a  yellow  or  pale  red  color,  which  became 
almost  white  after  recrystallisation.  This  description  is  entirely 
erroneous,  except  in  regard  to  the  pale  redness  of  the  salt. 

The  belief  in  the  existence  of  the  salt  (NHOaMnCh.HsO  rests 
on  the  authority  of  Rammelsberg  and  of  Pickering.  The  former 
states  that  it  crystallises  in  the  regular  system,  and  publishes  a 
partial  analysis  in  proof  of  the  formula  given  by  him.  His  figures 
are  as  follows : 

Found. 
21.03 


14.08 


100.00 

While  the  figures  obtained  in  the  case  of  ammonium  are  fairly 
close  to  those  calculated,  it  should  be  observed  that  in  the  case 
of  manganese  the  figures  found  are  about  ^  of  a  unit  nearer  to 
the  formula  with  fwo  molecules  of  water  of  crystallisation,  than  to 
that  given  by  Rammelsberg.  Pickering  obtained  a  salt  crystal- 
lising in  hard  brown  cubes,  which  after  recrystallisation  from  water 
gave  figures,  on  analysis,  which  "  corresponded  perfectly  to  the 
formula"  (NH4)«MnCl«.HiiO.  Unfortunately  these  figures  were 
not  published. 

In  regard  to  this  salt  a  series  of  experiments  was  carried  out, 
the  results  of  which  are  here  given.  The  samples  analysed  were 
obtained  under  widely  differing  conditions. 

I.  Obtained  by  rapid  cooling  of  a  solution  containing  manga- 
nous chloride  and  ammonium  chloride  in  proper  proportions  for 
the  formula  (NH4)9MnCl4. 


Calculated 

Mn 

21.97 

4CI 

56.52 

2NH4 

14-34 

HiO 

7.17 

nes 


13 


led  out, 
\d  were 

Imanga- 
lons  for 


0.6610  gram  gave  0.0985  gram  Mni04  (10.73  pc  cent.  Mn). 
0'2733  gram  gave  0.6521  gram  AgCl  (59.00  per  cent.  CI). 

II.  Obtained  by  spontaneous  evaporation  of  a  solution  of  the 
mixed  chlorides. 

0.3703  gram  gave  0.0771  gram  MntOi  (15.00  per  cent  Mn). 
0-3401  gram  gave  0.7668  gram  AgCl  (55.75  per  cent.  CI). 

III.  A  solution  was  evaporated  by  heat,  and  crystallisation 
allowed  to  take  place  by  slow  cooling. 

0.5497  gram  gave  aii6i  gram  Mni04  (15.21  per  cent.  Mn). 
0.2974  gran™  gave  0.6666  gram  AgCl  (55.43  per  cent.  CI). 

IV.  Prepared  by  the  same  method. 

0-3355  gran™  gave  0.0892  gram  MnsO«  (19.15  per  cent.  Mn). 
0.2298  gram  gave  0.4964  gram  AgCl  (53.42  per  cent.  CI). 

V.  Obtained  by  the  spontaneous  evaporation  of  a  solution  con- 
taining a  large  excess  of  manganous  chloride. 

0.3557  gram  gave  0.1008  gram  MmOi  (20.41  per  cent.  Mn). 
0.3693  gram  gave  0.7870  gram  AgCl  (52.70  per  cent.  CI). 

VI.  and  VII.  These  are  analyses  of  the  precipitate  first  men- 
tioned by  Godeffroy,*  which  is  produced  when  a  saturated  solu- 
tion of  manganous  chloride  in  concentrated  hydrochloric  acid  is 
added  to  a  similar  solution  of  ammonium  chloride.  As  this  pre- 
cipitate had  not  been  previously  analysed,  it  was  hoptfd  that  it 
might  prove  to  be  a  definite  compound.  It  is,  however,  a  mixture 
of  varying  composition.  Of  the  two  samples  obtained,  the  color 
of  the  second  was  much  more  decidedly  pink  than  that  of  the  first. 
They  were  both  dried  on  a  porous  plate,  and  then  to  constant 
weight  over  caustic  potash. 

VI.  Precipitated  by  mixing  solutions  at  ordinary  temperatures. 
0.3432  gram  gave  0.1056  gram  Mn304  (22.19  per  cent.  Mn). 
0.31 1 2  gram  gave  0.6572  gram  AgCl  (52.22  per  cent.  CI). 

VII.  Precipitated  by  mixing  solutions  previously  cooled  to 
about  o®. 

0.3667  gram  gave  0.1202  gram  Mn304  (23.61  per  cent.  Mn). 
0.3592  gram  gave  0.7367  gram  AgCl  (50.72  per  cent.  CI). 
These  results  form  a  series  in  which  the  percentage  of  manga- 
nese increases  and  that  of  chlorine  decreases,  as  here  arranged : 

>  Ber.  der  d.  chem,  Ges,  8.  g. 


14 


Mn. 

CI. 

I. 

10.73 

5900 

II. 

15.00 

5575 

III. 

15.21 

55.43 

IV. 

19.15 

53-42 

V. 

20.41 

52.70 

VI. 

22.19 

52.22 

VII. 

23.61 

50.72 

The  calculated  percentages  for  the  formula  (NHOiMnCU.HaO, 
using  accurate  atomic  weights,  are  Mn  21.90  and  CI  56.53.  It  is 
evident  that  no  such  salt  was  obtained.  Only  one  substance  in 
the  above  list  was  a  definite  compound,  namely  the  fifth,  already 
described  as  the  salt  (NH4)3MnCl4.2H90.  Its  crystalline  form 
was  definite.  I,  II  and  III  formed  indefinite  masses  of  ill-defined 
crystals.  VI  and  VII  were  amorphous  precipitates.  IV  crystal- 
lised, at  least  in  part,  in  perfectly  definite  octahedrons.  As  the 
analysis  showed  it  to  be  a  mixture,  it  appears  highly  probable 
that  the  octahedrons  consisted  of  impure  ammonium  chloride,  while 
the  remainder  of  the  deposit  contained  a  large  amount  of  the 
double  salt  with  two  molecules  of  water.  This  might  account  for 
the  fact  that  both  Rammelsberg  and  Pickering  state  that  the  salt 
obtained  by  them  is  regular  in  crystallisation.  Pickering  obtained 
cubes.  It  seems  probable  that  in  some  of  the  other  specimens 
recorded  in  the  above  list  manganous  chloride  was  present  as  a 
mechanical  admixture.  As  no  definite  directions  are  given  for 
the  preparation  of  the  salt  described  by  Rammelsberg  and  by 
Pickering,  absolute  proof  of  its  non-existence  can  hardly  be  ex- 
pected. The  investigation  above  related  seems,  however,  to  give 
sufficient  proof.  It  is  to  be  remembered  that  the  only  published 
analytical  evidence  which  is  really  in  favor  of  the  existence  of  the 
salt  consists  of  one  determination  of  the  ammonium. 

From  the  results  obtained  in  this  work  with  ammonium  chloride, 
the  conclusion  is  drawn  that  only  one  compound  of  that  substance 
with  manganous  chloride  has  ever  been  found,  namely  the  salt 
(NH08MnCh.2H»O. 


Experiments  with  Rubidium  Chloride, 

According   to    R.  Godeflfroy,'  rubidium   chloride  forms  with 
manganous  chloride  two  compounds,  differing,  however,  only  in 

>  Archiv  der  Pharmacie  [3I  \%,  47;  Zeitschr.  des  allg.  asterreichischen  Apotheker-Vereines, 
1875,  ai. 


16 


i.H.O. 
It  is 
nee  in 
ilready 
e  form 
defined 
rrystal- 
As  the 
robable 
e,  while 
;  of  the 
ount  for 
the  salt 
obtained 
ecimens 
»nt  as  a 
iven  for 
and  by 
y  be  ex- 
,  to  give 
iblished 
:e  of  the 


hloride, 

ubstance 

the  salt 


ms  with 
r,  only  in 

ter-Vereinef, 


the  amount  of  water  ot  crystallisation  contained  in  them.  One  is 
described  as  a  pale  rose-red,  crystalline  powder,  having;  the  com- 
position represented  by  the  formula  RbtMnCh.  By  recrystallising 
this  precipitate,  crystals  of  the  formula  Rb3MnCl4.3H<0  are  said 
to  be  obtained.  The  precipitate  was  here  investigated  first.  It 
is  obtained  by  bringing  together  concentrated  solutions  of  manga- 
nous  chloride  and  of  rubidium  chloride,  concentrated  hydro- 
chloric acid  having  been  used  as  the  solvent  in  both  cases.  The 
precipitate  was  prepared  several  times  under  slightly  different 
conditions  of  temperature.  It  every  case  it  was  dried  according 
to  the  method  already  described  under  the  experiments  with 
ammonium  chloride.  On  subsequent  heating  to  about  105**  in  an 
air-bath,  every  specimen  was  found  to  give  up  water  of  crystallisa- 
tion.   Partial  analyses  of  three  of  the  samples  are  here  recorded : 

I.  2.6691  grams  lost  at  los'-iio*  0.2395  gram  Ha0^8.97  per 
cent.  HaO. 

II.  0.51 20  gram  lost  at  105"-!  10*  0.0537  gram  H»0  :=  10.49  per 
cent.  HaO. 

Ill*  1.3399  grams  lost  at  105®-!  10°  0.1705  gram  HsO^  12.72 
per  cent.  HaO. 

The  precipitates  thus  dried  were  found  to  contain  varying 
amounts  of  chlorine. 

I.  0.3464  gram  gave  0.5408  gram  AgCl  (38.61  per  cent.  CI). 

II.  0.3134  gram  gave  0.5066  gram  AgCl  (40.10  per  cent.  CI). 

III.  0.3216  gram  gave  0.5591  gram  AgCl  (42.99  per  cent.  CI). 
If  these  percentages  of  chlorine  be  calculated  back  so  as  to 

represent  percentages  in  the  salt  before  the  combined  water  was 
driven  off,  they  become — 
!•  35- 1 5  per  cent.  CI. 
II.  35-89  per  cent.  CI. 
Ill-  37.52  per  cent.  CI. 

All  the  precipitates  were  very  pale  pink  in  color,  the  tint  being, 
however,  noticeably  darker  in  the  case  of  the  third  than  in  the 
others. 

The  figures  obtained  by  Godeflroy  are  as  follows  : 


Calculated  for  RbjMnCIj. 

Found. 

4C1 

38.71 

38.48 

Mn 

14.95 

14.00 

2Rb 

46.34 

45-97 

100.00 


98.45 


16 


From  a  consideration  of  all  the  above  facts  the  conclusion  is 
drawn  that  the  precipitate  produced  by  mixing  concentrated 
solutions  of  manganous  chloride  and  rubidium  chloride  in  con- 
centrated  hydrochloric  acid  is  not  anhydrous  and  is  not  a  single, 
definite  chemical  compound,  but  a  mechanical  mixture  of  variable 
composition.  These  conclusions  harmonize  with  those  arrived 
at  in  studying  the  similar  precipitate  produced  in  the  case  of 
ammonium  chloride. 

When  the  precipitate  is  dissolved  in  water  and  the  solution 
evaporated,  extremely  pale,  pink  crystals  are  obtained,  usually 
forming  radiating  groups.  This  substance  Godefiroy  found  to 
have  the  composition  represented  by  the  formula  RbiMnCl«.3H«0, 
the  salt  losing  two  molecules  of  water  at  loo^  and  the  remainder 
at  150".  After  working  on  this  salt  for  some  time  it  was  found  that 
it  encloses  a  considerable  amount  of  water  mechanically,  which  is 
only  given  off  with  extreme  slowness  in  a  desiccator,  unless  the 
salt  has  been  previously  thoroughly  powdered.  GodefTroy  does 
not  mention  having  taken  this  precaution,  and  it  therefore  seems 
probable  that  it  was  partly  owing  to  the  error  introduced  at  this 
point  that  his  analysis  led  to  the  formula  with  three  molecules  of 
water  instead  of  the  correct  one  with  only  two.  At  150"  the 
manganous  chloride  would  become  partly  oxidised,  and  thus  an 
additional  loss  in  weight — and  an  additional  error — would  be 
obtained.    Godeffroy's  figures  are  here  given : 

Calculated  for  RbgMnCli.jHjO.  Found, 

2Rb  40.53  ••• 

Mn  13.03  13.17 

4CI  33-65  33.83 

2H1O  8.76  8.54 

H.0  4.03  3.54 


100.00 

In  the  present  investigation  the  following  figures  were  obtained, 
the  salt  having  been  dried  to  constant  weight,  in  powdered  con- 
dition, over  calcium  chloride : 

0.3589  gram  gave  0.5099  gram  AgCl  (35.13  per  cent.  CI),  and 
0.0677  gram  MnsO«  (13.59  per  cent.  Mn). 

0.2856  gram  lost  at  105®-!  10"  0.0259  gram  H80  =  9.07  per 
cent.  HjO,  and  gave  0.1707  gram  RbCl  (42.24  per  cent.  Rb). 


I 


ilHIPl! 


17 


Calcul«i«(l  for 

Rb,MnCI,.aH,0. 

Found. 

?Rb 

170.4 

42.33 

42.24 

iVln 

54-8 

I361 

'3-59 

4CI 

141.48 

35-14 

35.13 

aH.O 

3592 

«.92 

9.07 

403.60  100.00  100.03 

The  composition  of  the  salt,  therefore,  corresponds  to  that 
required  by  the  formula  RbiMnCh.aHnO.  It  is  easily  soluble  in 
water  and  can  be  recrystallised.  It  readily  loses  all  its  water  of 
crystallisation  at  1 10**.  It  does  not  deliquesce  in  the  air,  and  does 
not  lose  its  water  of  crystallisation  when  placed  over  calcium 
chloride.  This  latter  point  needs,  perhaps,  further  discussion  in 
consideration  of  the  method  used  for  drying  the  salt  for  analysis. 
In  the  first  place  it  is  to  be  noted  that  the  salt  can  be  dried  in 
ordinary  dry  air,  provided  it  is  in  a  finely  powdered  condition, 
though  the  process  is  more  rapid  over  calcium  chloride.  That 
the  water  given  off  in  this  drying  is  not  water  of  crystallisation  is 
clear  from  three  considerations:  ist.  it  varies  in  amount;  2d.  on 
examining  a  crystal  of  the  salt  under  a  microscope,  inclusions  of 
water  can  be  seen ;  3d.  a  crystal  does  not  lose  its  form  or  trans- 
parency when  dried  over  calcium  chloride. 

Efforts  to  obtain  a  salt  corresponding  to  KMnCli.2HiO  were 
made,  but  no  such  rubidium  salt  was  found  even  when  a  consid- 
erable excess  of  manganous  chloride  was  present.  This  investi- 
gation shows  that,  in  all  probability,  the  only  definite  compound 
of  manganous  chloride  with  rubidium  chloride  which  is  capable  of 
isolation  is  the  salt  Rb3MnCl«.2H:0. 

Crystallography  of  the  salt. — It  is  obtained 
best  by  spontaneous  evaporation  of  the  aqueous 
solution.  The  crystals  frequently  form  radiating 
groups.  When  well  developed  they  form  elong- 
ated tabular  crystals.  In  habit  they  are  not 
always  the  same,  though  a  common  type  is  that 
represented  in  Fig.  5.  This  consists  of  two  indi- 
viduals twinned  and  united  along  a  plane  running 
parallel  to  the  long  axis  of  the  crystal.  The 
crystallisation  is  triclinic,  as  shown  by  the  optical 
properties  and  measurements  of  the  angles. 
There  is  no  reentrant  angle  formed  where  the 
Fio.  5.  two  parts  of  the  twin  unite,  hence  the  composi- 


18 


tion  face  is  not  a  crystallographic  plane.  The  substance  shows 
gliding  phenomena.  Its  crystallography  was  not  worked  out  in 
full.  The  measurements  made  are,  however,  pretty  accurate, 
and  it  is  believed  that  they,  together  with  the  rough  drawing,  will 
be  sufficient  for  the  satisfactory  identification  of  the  salt  at  any 
time.    The  cleavage  is  well  marked  parallel  to  the  plane  b. 

The  following  values  were  obtained  by  measurement : 

a: ^  =  84"  57'. 

a:*' =  95°  5'. 

a  './"=.  104°  41'. 

a:/' =  75°  16'. 

/:/'  (over  summit)  =  70"  36^'. 


a:jf  =169°  27'. 


b  :/^  U  :/'  =  138°  40}'  or  141"  42'.  The  presence  of  vicinal 
planes  made  the  true  value  of  this  angle  uncertain.  The  plane  g 
does  not  occur  on  the  other  side  of  the  crystal  at  the  same  end. 
Good  doubly-terminated  crystals  were  not  obtained. 


Experiments  with  Casium  Chlotide. 

In  the  papers  already  referred  to  Godeffroy  claims  to  have 
found  three  distinct  compounds  of  manganous  chloride  with 
caesium  chloride,  namely,  a  precipitate  CssMnCh  ttnd  two  crystal- 
line salts  Cs2MnCl4.3H«0  and  2(Cs»MnCl*).5H»0.  The  precipitate 
is  obtained  under  the  same  conditions  as  were  mentioned  in  the 
case  of  ammonium  chloride.  The  substance  was  prepared  three 
times  in  slightly  different  ways,  and  a  partial  analysis  was  made  in 
each  case.  On  drying  the  precipitate,  as  in  the  previous  experi- 
ments, over  caustic  potash,  a  constant  weight  was  not  obtained 
even  after  a  period  of  two  weeks.  It  is  evident  that  this  loss  was 
due  to  the  slow  abstraction  of  water  of  crystallisation.  The  deter- 
minations of  the  combined  water  are  necessarily  approximate  only. 
The  salt  was  dried  first  on  a  porous  plate,  and  then  for  a  few 
hours  over  caustic  potash  before  the  determination  was  made. 

I.  Solutions  slightly  warmed  at  the  time  of  precipitation  : 

0.6935  gram  lost  at  105°-!  10*  0.0804  gram  HsO=  11.59  per 
cent.  HaO. 

After  thus  drying,  0.31 16  gram  gave  0.0805  gram  MnoO*  (18.61 
per  cent.  Mn),  and  0.3001  gram  gave  0.4375  gram  AgCl  (36.05 
per  cent.  CI). 


19 


II.  Solutions  cooled  to  about  o*  at  the  time  of  precipitation : 
0.8523  gram  lost  at  105"-!  10"  0.0922  gram  HaO  =  10.82  per 

cent.  H»0. 

After  thus  drying,  0.3242  gram  gave  0.0843  grani  MnsO*  (18.73 
per  cent.  Mn),  and  0.3416  gram  gave  0.4991  gram  AgCl  (36.13 
per  cent.  CI). 

III.  The  solution  of  manganous  chloride  was  quite  dilute,  the 
acid  in  which  it  was  dissolved  being,  as  before,  concentrated. 

1. 1491  grams  lost  at  105°-!  10°  0.1189  gram  HaO  =  10.35  P^"^ 
cent.  H»0. 

After  thus  drying,  0.3589  gram  gave  0.0925  gram  MnsO*  (18.56 
percent.  Mn),  and  0.3032  gram  gave  0.4432  gram  AgCl  (36.15 
per  cent.  CI). 


2H.O 


Calculated  for 

Calculated  for 

CsMnClaaHaO. 

Found. 

CsMnCla. 

Found. 

1090 

11.59 
10.82 

10.35 

Mn 

18.66 

i8.6i 

18.73 
18.56 

3CI 

36.14 

36.05 
36.13 
36.15 

The  precipitate  consists  therefore  of  the  salt  CsMnCl8.2HsO  in 
almost  pure  condition.  After  drying  in  an  air-bath  at  105°  its 
composition  corresponds  to  the  formula  CsMnCls.  No  compound 
of  caesium  chloride  with  manganous  chloride  in  these  proportions 
has  hitherto  been  described.  The  results  which  Godeffroy 
obtained  by  analysis  of  the  precipitate,  prepared  in  the  same  way 
as  the  above,  are  : 

Calculated  for  Cs,MnCl4.  Found. 


2Cs 

Mn 
4CI 


57-47 
11.87 
30.66 

100.00 


57.76 
II. II 
31.04 

99.91 


He  seems  to  have  analysed  the  salt  only  once.  He  does  not 
state  the  manner  in  which  the  precipitate  was  dried.  No  explana- 
tion is  here  offered  to  account  for  the  disagreement  between  these 
results  and  those  obtained  in  the  present  investigation,  but  the 
author  feels  compelled  to  conclude  that  there  was  some  serious 
error  in  the  work  of  Godeffroy. 


20 


i 


The  pale  pink  precipitate  just  described  is  easily  soluble  in 
water.  When  the  solution  is  evaporated,  crystals  are  obtained  be- 
longing to  the  orthorhombic  system.  These  can  be  recrystallised 
and  are  then  found  to  be  in  pure  condition.  The  salt  is  pale  pink 
in  color.  It  is  not  deliquescent  in  the  air  under  ordinary  condi- 
tions ;  but,  when  powdered,  it  loses  its  water  of  crystallisation  in 
a  good  desiccator  over  calcium  chloride.  This  loss,  which  is  very 
slow,  has  already  been  referred  to  in  the  case  of  the  impure,  pre- 
cipitated salt.  It  gives  up  its  water  of  crystallisation  very  readily 
at  105°.  For  analysis  the  salt  was  dried  by  pressure  between 
layers  of  filtering  paper. 

0.5028  gram  lost  at  105°  o.0548gram  HaO  =  10.90  per  cent.  H»0. 

The  dried  salt  was  then  analysed. 

0.4212  gram  gave  0.1092  gram  Mn804  (18.67  P^^  c^"^*  ^>^)> 
and  0.2416  gram  CsCl  (45.29  per  cent.  Cs). 

0.4480  gram  gave  0.6547  gram  AgCl  (36.14  per  cent.  CI). 

Calculated  for  CsMnCl|.aHaO.  Found. 

2HsO  10.90  10.90 

Calculated  for  CsMnCl,.  Found. 

Cs  132.7  45.20  45.29 

Mn  54.8  18.66  18.67 

3CI  106. 1 1  36.14  36.14 


293.61  100.00  100.10 

The  crystallised  salt  has  therefore  the  formula  CsMnCk2H20, 
and  loses  all  of  its  water  at  105°. 

Crystallography  of  the  salt. — The  substance  forms  tabular  crys- 
tals, which  are  shown  by  their  optical  proper- 
ties and  angular  measurements  to  be  ortho- 
rhombic  (Fig.  6).  The  forms  observed  were, 
oP,  00  Poo ,  00  Poo ,  00  P  and  P2.  The  reflec- 
tions obtained  in  the  goniometer  were  not,  as 
a  rule,  very  good,  and  the  exact  values  of  the 
angles  are  rendered  additionally  doubtful  in 
some  cases,  owing  to  the  presence  of  vicinal 
planes. 

c  =:oP,  [001]. 

a  =ooPw,  [100]. 

^  =  00  Pw",  [010]. 

w=:«3P,  [no]. 

s  =:P2,  [122]. 


Fig.  6. 


21 


By  comparing  together  many  measurements  the  following 
values  were  obtained,  which  appeared  sufficiently  trustworthy  for 
the  determination  of  the  axial  ratios: 


s: 

a  =:ii6« 

14'. 

s: 

c  =124*' 

7'. 

s: 

S    =I27*> 

32'. 

m 

:^=I28*' 

6'. 

m 

tazrHi" 

54'. 

The  axial  ratios  deduced  are,  a  =  .7919,  3=  i,  <:^  1.2482. 
When  the  angles  given  above  are  calculated  from  these  axial 
ratios  they  become : 
s:a  =116*  14'. 
s:c  =124"  7'. 
s\s  =127®  32'. 
w:*=i28°  22i'. 


m 


a=i4i"'37i'. 


The  cleavage  is  parallel  to  a. 

If  caesium  chloride  be  added  to  a  solution  of  the  salt  CsMnCli. 
2H9O,  crystals  are  deposited,  on  evaporation,  which  are  quite  dif- 
ferent in  habit  from  those  previously  obtained,  and  are  much  paler 
in  color.  These  proved  to  be  the  salt  corresponding  to  that 
obtained  when  working  with  rubidium  chloride,  having  the 
formula  Cs»MnCU.2H»0.  This  is  probably  the  compound  ob- 
tained by  Godeffroy  and  regarded  by  him  as  two  different  salts, 
namely  CssMnCl4.3HaO  when  crystallised  out  of  an  aqueous 
solution,  and  2(Cs9MnCl4).5HsO  when  crystallised  out  of  a  solu- 
tion in  concentrated  hydrochloric  acid.  The  salt  is  not  deliques- 
cent in  ordinary  air,  and  retains  its  water  of  crystallisation  when 
dried  in  an  ordinary  desiccator.  For  analysis  it  was  dried,  in  the 
form  of  a  fine  powder,  over  calcium  chloride.  Its  water  of  crys- 
tallisation is  readily  driven  off  at  105°. 

0.431 1  gram  gave  0.0663  gram  MnsOi  (11.08  per  cent.  Mn),and 
0.2923  gram  CsCl  (53.53  per  cent.  Cs). 

0.2204  gram  lost  at  105"  0.0162  gram  H»0  =  7.35  per  cent. 
HaO,  and  gave  0.2532  gram  AgCl  (28.41  per  cent.  CI). 

Calculated  for  CsaMnCl^.aHaO.  Found. 

^  265.4  53.34  53.53 

Kin  54.8  ii.oi  11.08 

4CI  141.48  28.43  28.41 

2HaO  35.92  7.22  7.35 


497.60 


100.00 


100.37 


\s 


22 


■il 


m 


The  salt  corresponds  in  composition  to  the  formula  CssMnCh. 
2H1O.  GodefTroy's  analyses  of  this  salt,  which  seemed  to  indicate 
the  presence  of  three  molecules  of  water,  were  no  doubt  vitiated 
by  the  incomplete  drying  of  the  salt  before  analysis,  as  was 
pointed  out  in  the  case  of  the  corresponding  rubidium  compound. 
His  figures  are : 

Calculated  for  CsgMnCU.sHgO.  Found. 

2Cs  51.39 

Mn  10.65 

4CI  27.50 

SHiiO  10.46 


10.07 
27.24 
10.96  and  10.23 


100.00 


No  evidence  was  found  in  favor  of  the  existence  of  a  salt  of  this 
composition. 

Crystallography  of  the  salt  Cs»MnCl4.2HjO. — This  was  not 
worked  out  in  full,  but  the  following  details  are  given  to  serve  for 
the  identification  of  the  substance.  It  is  triclinic 
in  crystallisation,  resembling,  in  general  appear- 
ance, the  corresponding  rubidium  salt.  The 
cleavage  is,  however,  parallel  to  the  best  devel- 
oped face,  a,  which  is  not  true  of  the  rubidium 
compound.  Another  difference  between  the  two 
salts  is  observed  in  regard  to  the  method  of 
twinning.  The  caesium  salt  shows  a  reentrant 
angle  of  about  169°  where  the  two  individuals 
are  joined,  while  the  rubidium  salt  does  not. 
Other  differences  are  evident  from  the  measure- 
ments. Fig.  7  gives  a  rough  drawing  of  a  crystal 
of  this  salt,  not  twinned.  Most  of  the  measurements  here  given 
are  the  mean  of  two,  made  on  different  crystals.  They  generally 
agreed  within  a  few  minutes.  The  last  two  are  only  approximate. 
The  plane  g  occurs  only  on  one  side  of  the  crystal  at  each  end. 
The  following  measurements  were  obtained : 
a:b  =. 95°  27'  (hence  a\b'  =  84°33'). 

« :jr  =  139°  24'. 

b'.e  =151°  6'. 

d':^=i54°ii'. 

^ :  e' (over  summit)  =  54°  53i'. 

a\e  =851°. 

a:tf'  =  97i°. 


Fig.  7. 


23 


A  careful  attempt  was  made  to  prepare  the  salt  2(Cs9MnCh). 
sHsO  by  following  the  directions  of  Godeffroy  as  closely  as  pos- 
sible. The  solution  in  concentrated  hydrochloric  acid,  which 
remained  over  the  precipitate  of  slightly  impure  CsMnCl3.2H20, 
was  evaporated  without  the  aid  of  heat,  by  drawing  a  stream  of 
dry  air  over  it  for  several  months.  A  few  small  crystals  were  at 
length  obtained.  These  were  very  pale  pink  in  color  and  seemed 
to  be  the  salt  CsjMnCl4.2HsO.  On  attempting  to  isolate  the  com- 
pound, after  further  evaporation  of  the  solution,  it  was  found  that 
some  other  substance,  probably  manganous  chloride,  had  crystal- 
lised out  as  well.  As  it  was  evidently  impossible  to  obtain  a  pure 
product  without  recrystallisation,  which  would  have  been  to  depart 
from  the  conditions  mentioned  by  Godeffroy,  the  subject  was  not 
followed  up.  In  view  of  the  existence  of  the  salt  CsjMnCl4.2H20 
and  of  the  non-existence  of  the  salt  CsaMnCK.sHsO  described  by 
Godeffroy,  and  in  view  of  the  weak  evidence  brought  forward  to 
prove  the  existence  of  the  salt  2(Cs2MnCl4).5HaO,  the  matter  did 
not  seem  worthy  of  further  investigation.  The  existence  of  the 
salt  under  consideration  seems  in  the  highest  degree  improbable 

Experiments  with  Magnesium  Chloride  and  with  Magnesium 

Bromide. 

In  this  part  of  the  work  it  was  found  more  satisfactory  to  use 
alcohol  and  water,  instead  of  water  alone,  as  a  solvent.  Seventy 
per  cent,  of  alcohol  is  probably  about  the  best  strength.  The 
solutions  were  always  kept  acidified  to  prevent  the  decomposition 
of  the  magnesium  salt.  When  a  solution  of  manganous  chloride 
and  magnesium  chloride  is  evaporated  the  two  chlorides  unite, 
forming  one  or,  perhaps,  more  compounds,  the  appearance  of 
which  varies  greatly  according  to  the  exact  conditions  of  forma- 
tion. Many  experiments  were  performed.  In  general  a  compound 
was  obtained  crystallising  in  flattened,  sometimes  feather-like 
crystals,  which  were  never  found  to  be  pure.  On  one  occasion 
these  plates  were  left  standing  for  several  weeks  in  contact  with 
the  mother-liquor,  and  were  found  to  be  entirely  transformed  into 
crystals  almost  round  in  shape,  usually  about  i  cm.  in  diameter. 
They  could  not  be  investigated  crystallographically,  owing  to 
their  rapid  deliquescence.  Though  not  obtained  in  pure  con- 
dition, analysis  shows  that  this  salt  corresponds  in  composition  to 
the  bromide,  described  below,  which  is  much  more  easily  worked 


24 


with.  The  flattened  crystals  of  the  chloride  seem  to  have  the 
same  composition  as  the  rounded  ones,  though  they  were  never 
obtained  in  a  condition  approaching  purity.  As  this  double 
chloride,  in  whatever  form  it  is  obtained,  is  deliquescent  in  the  air 
and  loses  some  of  its  water  of  crystallisation  over  calcium  chloride, 
a  satisfactory  analysis  of  it  could  not  be  made.  It  was  dried  for 
a  few  hours  in  a  desiccator,  but  was  found  when  analysed  to  con- 
tain, still,  a  considerable  amount  of  hygroscopic  water.  For  the 
method  of  analysis  see  below. 

0.7608  gram  gave  0.1981  gram  MniO*  (18.76  per  cent.  Mn),  and 
0.1569  gram  Mg«PaOi  (4.50  per  cent.  Mg). 

0.9970  gram  gave  1.4961  grams  AgCl  (37.11  per  cent.  CI). 

The  water  of  crystallisation  is  not  all  given  off  without  decom- 
position of  the  salt. 

Calculated  for  MngMgClfiaH,0.  Found. 

109.6  19.52  18.76 

24.21  4.31  4.50 

212.22  37"79  37*  1 1 

215.52  38.38 


2Mn 
Mg 
6C1 
12H.O 


|i    t 


561.55  100.00 

If  we  allow  for  the  hygroscopic  water,  which  seems  to  be  present, 
it  per  cent.,  we  obtain  Mn  19.15,  Mg  4.59  and  CI  37.88  per  cent. 
The  salt,  though  somewhat  impure,  evidently  corresponds  in 
composition  to  the  bromide  mentioned  below,  and  has  the  formula 
Mn»MgCl6.i2H«0. 

As  noticed  near  the  commencement  of  this  paper,  when  a  large 
excess  of  manganous  chloride  is  present  the  salt  MnCl:.2H90  is 
produced.  No  evidence  was  found  of  the  existence  of  a  salt  con- 
taining manganous  chloride  and  magnesium  chloride  in  the  pro- 
portions of  one  molecule  to  one. 

When  manganous  bromide  and  magnesium  bromide  are  present 
in  a  solution  in  the  proportion  of  two  molecules  of  the  former  to 
one  of  the  latter,  and  the  solution  is  evaporated,  a  double  salt 
crystallises  out  on  cooling.  The  substance  usually  forms  a  com- 
pact mass  of  red  crystals  at  the  bottom  of  the  beaker.  It  can  be 
recrystallised,  but  well-formed,  individual  crystals  are  seldom 
obtained.  It  is  deliquescent  in  the  air.  No  loss  of  water  of 
crystallisation  was  observed  when  it  was  dried  over  calcium 
chloride.    The  most  convenient  method  found  for  the  separation 


26 


of  the  metals,  in  analysis,  was  as  follows  :  Decompose  the  salt 
with  a  small  amount  of  sulphuric  acid,  and  heat  till  all  the  hydro- 
chloric (or  hydrobromic)  acid  is  driven  off;  then  add  a  solution 
of  ammonium  chloride,  and  heat  nearly  to  boiling.  Add  gradually 
ammonium  sulphide  free  from  carbonate.  Keep  hot  for  about  an 
hour,  and  then  filter  and  wash.  The  manganous  sulphide  is  then 
dissolved  in  dilute  hydrochloric  acid,  filtered  free  from  sulphur, 
and  precipitated  as  carbonate  after  driving  off  the  hydrogen  sul- 
phide. The  solution  containing  the  magnesium  is  evaporated, 
acidified,  filtered  from  sulphur,  and  the  magnesium  then  precipi- 
tated in  the  usual  way. 

The  water  of  crystallisation  present  in  this  salt  cannot  be  deter- 
mined directly  on  account  of  the  decomposition  of  the  substance. 
That  decomposition  actually  takes  place  before  all  the  water  is 
given  off  is  evident  from  the  darkening  in  color,  and  the  fact  that 
part  of  the  salt  is  rendered  insoluble  in  water.  The  substance 
was  obtained  in  almost  pure  condition  without  recrystallisation,  as 
shown  by  the  following  figures  obtained : 

0.6679  gram  gave  0.1235  gram  Mns04  (13.32  percent.  Mn),  and 
0.0915  gram  MgsPaOi  (2.99  per  cent.  Mg). 

0.6654  gram  gave  0.8998  gram  AgBr  (57.55  per  cent.  Br). 

After  heating  the  salt  for  several  hours  not  far  above  lOo",  and 
then  for  seven  hours  at  about  150",  the  loss  in  weight  represented 
16.27  per  cent,  of  water.  Considerable  decomposition  had  taken 
place. 

Calculated  for  MngMgBrg.iaH^O.  Found. 

2Mn  109.6  i3'24  i3'32 

Mg                         24.21  2.93  2.99 

6Br  478.56  '        57-80  57.55 

i2H»0  215.52  26.03 


i 

i 


827.89  100.00 

The  formula  of  the  salt  is  therefore  MnjMgBr«.i2HsO,  corres- 
ponding to  that  of  the  impure  chloride  obtained. 


Negative  Results. 

No  compound  of  lithium  chloride  with  manganous  chloride  was 
found,  but  it  is  worthy  of  note  that  the  aqueous  solution  of  the 
mixed  chlorides  has,  when  concentrated,  a  green  color,  which 
becomes  quite  brilliant  when  the  solution  is  heated.    When  potas- 


26 


sium  chloride  is  present  instead  of  lithium  chloride,  the  hot  solu- 
tion appears  greenish-brown. 

Some  evidence  of  the  formation  of  a  compound  of  sodium 
chloride  with  manganous  chloride  was  obtained,  but  it  was  not 
found  possible  to  isolate  the  product  in  sufficiently  pure  condition 
for  analysis,  owing  to  the  very  great  excess  of  manganous  chloride 
present. 

Unsuccessful  attempts  were  made  to  obtain  compounds  of  man- 
ganous chloride  with  the  chlorides  of  copper  (cuprous  and  cupric), 
calcium,  strontium  and  barium.  A  concentrated  solution  of  the 
mixed  chlorides  of  calcium  and  manganese  possesses  a  green 
color,  somewhat  like  that  observed  in  the  case  of  lithium  chloride. 
An  almost  amorphous  mass  was  obtained,  containing  manganous 
chloride  and  calcium  chloride,  which  may  have  been  an  impure 
double  salt,  but  it  was  not  in  a  fit  condition  for  analysis. 

Conclusion. 

The  work  was  not  continued  beyond  magnesium.  Compounds 
have,  however,  been  described  of  manganous  chloride  with  cad- 
mium chloride'  and  with  mercuric  chloride."  We  find,  then,  that 
manganous  chloride  combines  with  the  chlorides  of  potassium, 
rubidium  and  caesium  ;  but  that,  following  the  families  according 
to  the  periodic  system,  there  is,  after  caesium,  a  gap  of  considerable 
length,  including  chiefly  the  chlorides  of  calcium,  strontium  and 
barium.  Manganous  chloride  appears  incapable  of  combining 
with  any  of  the  chlorides  between  caesium  and  magnesium.  The 
latter,  however,  marks  the  commencement  of  a  new  series,  with 
every  member  of  which  manganous  chloride  can  probably  com- 
bine. The  explanation  of  these  facts  is  simple  if  we  assume  that 
the  acidic  and  basic  powers  of  manganous  chloride  are  about 
equal  to  those  of  strontium  chloride,  and  that  in  its  compounds 
with  the  chlorides  of  potassium,  rubidium  and  caesium,  manganous 
chloride  acts  in  its  acidic  capacity,  while  in  its  compounds  with  the 
chlorides  of  magnesium  (zinc?),  cadmium,  etc.,  it  acts  in  its  basic 
capacity.  Taking  this  view  we  should  expect  a  break  to  occur 
between  these  two  series. 

The  compounds  hitherto  described  are  given  in  tabular  form  at 
the  commencement  of  the  paper.  A  comparison  between  that  list 
and  the  one  given  below,  of  the  compounds  actually  found  to 


1  V.  Hauer,  Jour,  fiir  pr,  Chem.  68,  393. 


>  V,  Bonsdorff,  Pogg.  Ann.  17, 347. 


27 

exist,  will  show  that  the  regularity  in  the  series  is  much  greater 
than  was  to  be  supposed. 

KMnCl».2HO  (tricl.)  

(NH4).MnCl«.2H.O  (monocl.) 

(RbiMnCl4.2H.O  (tricl.) 

CsMnCh  2H«0  (orthorh.)  (Cs>MnCl4.2H20  (tricl.) 

MmMgCl«.i2H90 

Mn.MgBr6.i2HjO. 
It  will  be  noticed  that  these  salts  are  very  irregular  from  a  crys- 
tallographic  standpoint.  It  is  strange  that  two  gaps  should  occur 
in  the  left-hand  series.  Special  efforts  were  made  to  obtain  both 
of  the  missing  compounds,  but  without  success.  Perhaps  the 
entire  dissimilarity  in  crystal  system  and  habit  between  the  potas- 
sium and  the  caesium  salt  may  be  taken  as  evidence  that,  though 
chemically  analogous,  the  two  compounds  are  not  really  very 
closely  related  to  each  other. 


Part  II. 

Antimony  Compounds, 

Since  two  double  chlorides  containing  antimony  had  been 
described  by  Godeffroy  as  containing  six  molecules  of  alkali 
chloride  to  one  of  antimony  chloride,  and  were  therefore  to  be 
regarded  as  exceptions  to  the  general  rule  governing  the  compo- 
sition of  the  double  halides,  it  was  thought  best  to  repeat  the 
work  of  Godeffroy.  The  exceptional  salts  referred  to  are 
SbCl8.6CsCl    and    SbCh.eRbCl. 

Experiments  with  Casium  Chloride. 

It  is  necessary,  first  of  all,  to  give  a  brief  review  of  the  work  of 
Godeffroy  on  this  subject.  In  1874'  he  published  the  first  state- 
ments in  regard  to  the  precipitate  obtained  by  mixing  solutions 
of  antimony  chloride  and  caesium  chloride  in  concentrated  hydro- 
chloric acid.  This  precipitate  was  recrystallised  several  times  and 
analysed.  The  mean  of  five  analyses  gave  him  the  following 
results:'  Chlorine,  33.419  per  cent. ;  antimony,  30.531  per  cent. 
From  these  figures  he  derives  the  formula  SbCl».CsCl.    The 

1  Zeitschr.  des  allg,  osterr.  Apothek«r-Vereines,  1874, 161. 
'  Ber.  der  d,  chem.  Ges.  1, 375. 


numbers  calculated  from  the  formula  are :  Chlorine,  35.93  per 
cent. ;  antimony,  30.37  per  cent.  Godeffroy  regarded  the  precipi- 
tate and  the  crystalline  salt  as  identical  in  composition,  but  gives 
no  definite  proof  in  support  of  this  idea.  In  the  year  following ' 
he  published  a  complete  analysis  of  the  salt,  assigning  to  it  an  en- 
tirely new  formula,  namely,  SbCia.6CsCl.  The  results  he  gives 
are  as  follows : 

Calculattd  for  SbCI|.6CsCl.        Found. 

9CI  25.77  25-68 

Sb  9.83  9.40 

6Cs  64.40  63.98 


100.00 


99.06 


While  the  figures  found  agree  fairly  well  with  those  calculated, 
the  fact  must  not  be  lost  sight  of  that  there  is  a  discrepancy  be- 
tween the  figures  found  in  1874  and  those  found  in  1875  of  over 
seven  units  in  the  case  of  chlorine  and  of  over  twenty-one  units 
in  the  case  of  antimony.  As  no  explanation  of  this  difference 
is  given,  it  seems  necessary  to  attribute  it  to  experimental  errors 
in  analysis.  The  methods  used  in  the  later  investigation  are 
worthy  of  notice  in  this  connection.  The  salt  was  dissoh'ed  in 
water  acidified  with  tartaric  acid,  and  after  precipitation  :f  the  chlo- 
rine as  silver  chloride,  the  antimony  was  precipitated  aa  sulphide. 
The  sulphide  was  then  oxidised  with  nitric  acid,  and  the  sulphuric 
acid  thus  obtained  was  estimated  in  the  usual  way.  The  amount 
of  antimony  was  then  calculated  from  the  amount  of  barium 
sulphate  obtained. 

In  the  present  investigation  the  precipitate  was  prepared  in  the 
manner  described,  the  conditions  of  temperature  being,  however, 
slightly  varied  in  the  different  experiments.  The  antimony  chlo- 
ride used  for  the  first  was  purified  by  precipitation  as  oxychloride, 
that  for  the  second  by  distillation.  The  precipitate  of  the  double 
salt  is  very  pale  yellow  in  color.  This  does  not  appear  to  be  due 
to  impurities.  The  crystallised  salt  has  the  same  color.  The 
precipitates  were  dried  for  analysis  in  the  manner  before  described. 
The  methods  of  analysis  will  be  referred  to  later  on  in  the  paper. 

I.  0.6051  gram  gave  0.2146  gram  SbsSs  (25.32  per  cent.  Sb), 
and  0.3162  gram  CsCl  (41.26  per  cent.  Cs). 

II.  0.7470  gram  gave  0.26S2  gram  SbsS«  (25.63  per  cent.  Sb), 
and  0.3880  gram  CsCl  (41.01  per  cent.  Cs). 

I  Zeitschr.  des  allf;.  Osterr.  Apotheker-Vereines,  1S75,  at. 


29 


A  third  preparation  of  the  precipitate,  usinjj  the  same  redistilled 
antimony  chloride  as  was  used  for  the  second,  gave  25.38  per  cent, 
of  antimony.  The  composition  of  the  precipitate  appears  therefore 
to  be  nearly  constant.  The  figures  obtained  correspond  pretty 
closely  to  those  required  for  a  salt  of  the  formula  2SbClii.3CsCl. 

Calculated  for  Ci,Sb,CI,.  Found. 

Sb  25.03  25.32  25.63 

Cs  41.66  41.26  41.01 

This  precipitate  is  soluble  in  hot  dilute  hydrochloric  acid,  though 
only  slightly  soluble  in  the  cold.  On  evaporation,  crystals  of 
various  habits  are  obtained  according  to  the  conditions.  They 
generally  appear  as  needles  or  thin  prisms  when  deposited  by  the 
cooling  of  a  hot  solution  ;  while  by  spontaneous  evaporation  they 
form  thicker  prisms  or  irregular  plates,  having  a  rough  pseudo- 
hexagonal  appearance  produced  by  twinning.  Two  or  three 
different  samples  of  the  crystallised  salt  were  analysed.  The 
composition  of  all  of  them  agreed  with  the  formula  proposed. 

0.31 1 2  gram  gave  0.1641  gram  CsCl  (41.63  per  cent.  Cs). 

0.1940  gram  gave  0.0684  gram  SbsSa  (25.16  per  cent.  Sb). 

0.2059  gram  gave  0.2770  gram  AgCl  (33.27  per  cent.  CI). 

0.4237  gram  gave  0.1499  gram  SbvSa  (25.25  per  cent.  Sb),  and 
0.2240  gram  CsCl  (41.74  per  cent.  Cs). 

0.2203  gram  gave  0.2938  gram  AgCl  (32.97  per  cent.  CI). 

Calculated  for  CsgSbgClg. 

3Cs  398.1  41.66 

2Sb  239.2  25.03 

9CI  318-33  33-31 


Found. 

41.63  41.74 

25.16  25.25 

33-27  32-97 


955-63        100.00  100.06 

As  this  salt  was  obtained  with  the  greatest  ease  and  according 
to  the  method  described  by  Godeffroy,  the  author  feels  justified 
in  drawing  the  conclusion  that  this  is  the  compound  for  which 
Godeffroy  proposed  the  formula  SbCh.CsCl  and,  later,  SbCls. 
6CsCl,the  correct  formula  being  CsaSbsCU.  This  salt  is  therefore 
no  longer  to  be  considered  as  an  exception  to  the  general  rule 
regarding  the  composition  of  the  double  halides.  This  is  the  only 
compound  of  caesium  chloride  and  antimony  chloride  which  is 
easily  obtained.  It  may  be  that  a  salt  of  the  formula  CsSbCU 
could  be  produced  under  suitable  conditions,  but  the  salt  above 


80 


described  was  the  only  one  identified  in  the  present  investigation, 

though  efforts  were  made  to  obtain  others. 
The  crystallography  of  this  salt  was  not  worked  out.    A  few 

details  were,  however,  obtained.  It 
usually  crystallises  in  elongated 
prisms.  These  belong  to  the  ortho- 
rhombic  system,  but  are  sometimes 
twinned,  when  very  short,  in  such  a 
way  as  to  give  a  rough  pseudo-hex- 
agonal form.  Such  a  twin  is  repre- 
sented in  Fig.  8.  The  three  individ- 
uals combined  in  the  crystal  can  be 
distinguished  by  examination  in  paral- 
lel polarised  light. 


Fio.  8. 


Experiments  with  Rubidium  Chloride. 

By  evaporation  of  a  dilute  hydrochloric  acid  solution  containing 
antimony  chloride  and  rubidium  chloride,  Godeffroy'  obtained 
tabular  crystals  of  a  double  salt,  to  which  he  gave  the  formula 
SbCl>.6RbCl.  This  was  analysed  by  the  same  method  as  that 
described  under  caesium  chloride.  The  following  are  the  figures 
given  by  Godeflfroy : 

Calculated  for  SbCI|.6RbCI.  Found. 

9CI  3347  3345 

Sb  12.79  13.10 

6Rb  53.74  53.06 


100.00 


99.61 


A  substance  corresponding  to  Godeffroy 's  description  was  easily 
obtained  by  following  his  directions,  and  crystallised  out  of  the 
solution  in  dilute  hydrochloric  acid  in  beautiful,  colorless,  six-sided 
plates,  tables,  or  thicker  crystals,  according  to  the  conditions. 
The  salt  has  a  very  strong  crystallising  force.  It  is  readily  soluble 
in  dilute  hydrochloric  acid,  but  less  so  in  the  concentrated  acid. 

By  mixing  concentrated  solutions  of  rubidium  chloride  and  of 
antimony  chloride  in  concentrated  hydrochloric  acid,  the  double 
salt  is  formed  as  a  distinctly  crystalline  precipitate.  Repeated 
analyses  show  that  the  composition  of  this  salt  does  not  corres- 


1  Zeitschr.  des  allg.  osterr.  Apotheker-Vereines,  18751  at. 


81 


pond  to  the  formula  proposed  by  Godeffroy.  The  substance  was 
prepared  under  varyinj?  conditions,  being  crystallised  out  either 
by  slow  cooling  of  the  s  )lution,  or  by  sudden  cooling,  or  by  spon- 
taneous evaporation.  In  the  first  experiment  the  two  chlorides 
were  mixed  in  the  proportions  required  by  the  formula  of 
Godeffroy.  In  the  other  cases  no  special  care  was  taken  in 
regard  to  the  proportions.  The  composition  of  the  salt  formed 
did  not  vary  appreciably.  All  the  analyses  made,  in  this  part  of 
the  investigation,  are  here  given,  except  one  attempt  to  determine 
rubidium  as  nitrate,  which  was  quite  untrustworthy.  The  varia- 
tions from  ihe  normal  composition  are  no  doubt  due  to  experi- 
mental errors,  or  to  the  presence  of  slight  impurities  in  some 
specimens  of  the  salt. 

I.  0.5720  gram  gave 0.1902  gram  SbsSa  (23.73  per  cent. Sb),  and 
0.8538  gram  AgCl  (36.91  per  cent.  CI). 

II.  0.4174  gram  gave  0.1401  gram  SbsSa  (23.96  per  cent.  Sb), 
and  0.2297  gram  RbCl  (38.89  per  cent.  Rb). 

0'3i90  gram  gave  0.4772  gram  AgCl  (36.99  per  cent.  CI). 

III.  0.4028  gram  gave  0.1348  gram  SbsSt  (23.89  per  cent.  Sb), 
and  0.6007  gram  AgCl  (36.88  per  cent.  CI). 

0.6881  gram  gave  0.3769  gram  RbCl  (38.71  per  cent.  Rb). 

IV.  0.2728  gram  gave  0.4071  gram  AgCl  (36.90  per  cent.  CI). 

V.  0.3359  gram  gave  0.1125  f^'^ani  SbsSs  (23.90  per  cent.  Sb), 
and  0.1850  gram  RbCl  (38.92  pei  cent.  Rb). 

A  tabular  view  of  these  rt?sults  will  make  the  matter  clearer. 


PBlriitaf#Hl  ft%r 

Found  by 
Godeffroy. 

Found  by  the  Author. 

SbCI,.6RbCI. 

1. 

II. 

III. 

IV  and  v. 

Sb        12.60 

I3-IO 

2373 

23.96 

23.89 

23.90 

6Rb     53.86 

5306 

... 

38.89 

38.71 

38.92 

9CI       33-54 

3345 

36.91 

36.99 

36.88 

36.90 

These  figures  show  that  the  salt  obtained  in  the  present  investi- 
gation is  a  definite  chemical  compound,  which  does  not  correspond 
in  composition  to  the  numbers  calculated  from  Godeffroy 's  formula. 
That  this  salt  is  really  identical  with  that  obtained  by  Godeffroy, 
in  spite  of  the  great  difference  between  the  analytical  results  in 
the  two  cases,  is  proved  by  several  considerations.  This  salt  is 
obtained  with  the  greatest  ease,  much  more  readily  than  any  othsr 

>  These  figures  differ  slightly  from  those  calculated  by  Godeffroy,  owing  to  the  use  of  different 
atomic  weights  in  the  two  cases. 


32 


compound  of  rubidium  chloride  with  antimony  chloride.  Of 
the  three  salts  found  this  one  contains  the  largest  percentage  of 
rubidium,  and  therefore  approaches  more  nearly  than  either  of  the 
others  to  the  composition  required  by  Godeffroy's  formula.  The 
directions  of  Godeflfroy  were  followed  closely  in  preparing  the 
salt,  and  in  one  case  at  least  the  two  chlorides  were  present  in 
solution  in  the  proportions  required  by  the  above  formula.  The 
salt  was  examined  :rystallographically  by  Streng.'  He  describes 
it  as  forming  hexagcnal  tables  by  a  combination  of  the  basal  plane 
and  fundamental  pyramid,  with  a  very  slight  development  of  the 
fundamental  prism.  In  the  present  investigation  no  distinct 
development  of  the  prism  was  observed.  The  pyramid  faces  were 
strongly  striated  in  a  horizontal  direction,  so  that  accurate  measure- 
ments were  impossible.  The  mean  of  three  measurements  of 
P :  P  over  a  middle  edge  gave  him  129°  30',  from  which  he  calcu- 
lated the  axial  ratio  a:c  as  i :  1.836.  The  crystals  obtained  in 
the  present  investigation  agree  with  the  description  of  Streng. 
The  angle  measured  by  him  was  here  found  to  vary  between  127** 
and  131*,  though  the  striations  on  the  crystals  prevented  anything 
but  the  roughest  measurements.  Stauroscopic  examination  shows 
that  the  crystals  are  not  really  hexagonal  in  crystallisation ;  but  as 
Streng  does  not  seem  to  have  examined  his  crystals  optically,  this 
disagreement  in  regard  to  the  crystal  system  cannot  be  con- 
sidered as  evidence  in  favor  of  the  two  salts  being  diflerent. 
The  substance  as  prepared  in  this  investigation  was,  to  all  out- 
ward appearance,  hexagonal  in  crystallisation,  and  agreed  exactly, 
except  in  the  points  mentioned,  with  the  descriptions  given  by 
Godeffroy  and  by  Streng.  There  can  therefore  be  little  doubt 
that  the  substances  as  obtained  in  the  two  investigations  were 
identical.  The  conclusion  is  therefore  drawn  that  no  salt  exists 
having  the  formula  SbCl8.6RbCl. 

As  the  five  partial  analyses  already  given  showed  that  the 
formula  of  the  salt  was  by  no  means  simple,  the  matter  was  taken 
up  again,  with  a  view  to  obtaining  a  quantity  of  the  salt  in  as  pure 
a  condition  as  possible,  and  then  making  several  analyses. 
Having  prepared  a  considerable  amount  of  the  substance,  it  was 
recrystallised  five  times  from  dilute  hydrochloric  acid.  In  the 
last  two  crystallisations  the  solution  was  cooled  rapidly,  so  that 
the  salt  Was  deposited  in  very  small,  six-sided  scales,  possessing 

>  Archiv  der  Pharmacie  [3]  9>  343. 


33 


a  beautiful,  pure  white,  lustrous  appearance.  The  final  drying  of 
the  compound  was  as  follows :  It  was  first  of  all  dried  by  pressure 
between  layers  of  filtering  paper  previously  washed  with  hydro- 
chloric acid,  and  was  then  finely  powdered  and  placed  on  a  watch- 
glass  in  a  desiccator  over  phosphorus  pentoxide.  It  was  weighed 
from  day  to  day  until  the  loss  in  twenty-four  hours  was  not  per- 
ceptible, the  weighings  being  made  to  the  tenth  of  a  milligram. 
In  this  way  over  two  grams  of  the  salt  were  obtained.  The 
methods  of  analysis  used  are  now  to  be  described.  In  nearly 
all  the  analyses  of  salts  containing  antimony,  the  methods  used 
were  essentially  the  same  as  those  here  given. 

The  salt  was  dissolved  in  dilute  hydrochloric  acid  in  an  Erlen- 
meyer  flask  and  the  solution  heated  to  incipient  boiling.  Carefully 
washed  hydrogen  sulphide  was  then  passed  in  until  the  solution 
was  nearly  cold.  The  flask  was  then  tightly  closed  and  left  for  at 
least  an  hour,  when  it  was  heated  again  to  about  60".  The  anti- 
mony sulphide  was  collected  in  a  Gooch  crucible,  the  filtration 
being  performed  while  the  liquid  was  hot.  The  precipitate  was 
then  washed  with  freshly  prepared  hydrogen  sulphide  water  and 
afterward  dried  for  about  an  hour  at  105°.  The  crucible  was  then 
placed  in  a  small  air-bath  filled  with  carbon  dioxide,  into  which  a 
current  of  the  washed  and  dried  gas  was  kept  passing.  The  tem- 
perature of  this  bath  was  slowly  raised  to  200°  and  the  flame  then 
extinguished.  The  sulphide  of  antimony  obtained  in  this  way 
was  black  and  anhydrous.  It  was  found  that  all  the  water  can  be 
driven  off"  from  the  sulphide  without  converting  it  into  the  black 
form,  but  the  process  is  very  slow.  When  the  black  sulphide 
was  heated  to  20o"'-22o°  for  a  few  hours  a  slight  loss  in  weight 
was  observed  in  almost  all  cases.  This  may  have  been  due  to  the 
decomposition  of  a  minute  quantity  of  oxychloride  of  antimony 
present.  One  precipitation  of  the  sulphide  (the  fourth)  was  made 
after  adding  a  small  quantity  of  tartaric  acid  to  the  solution.  The 
precipitate  formed  in  this  case  also  suffered  a  very  slight  loss  in 
weight  on  continued  heating.  If  the  presence  of  oxychloride  of 
antimony  be  the  cause  of  this  reduction  in  weight  it  proves  that, 
under  the  conditions  mentioned,  excess  of  hydrogen  sulphide 
does  not  entirely  decompose  oxychloride  of  antimony,  even  when 
acting  for  so  long  a  time  as  three  hours  on  the  precipitate,  the 
solution  being  kept  warm  during  one  hour.  The  first  weighing 
of  the  precipitate  was  the  one  assumed  to  be  correct  in  every 


34 


case.  The  subsequent  loss  in  weight  was  so  slight  (usually  about 
one-tenth  of  a  milligram  in  half  an  hour's  heating  at  210°),  that 
no  great  error  can  have  been  introduced  by  neglecting  it,  what- 
ever may  have  been  its  actual  cause.  The  use  of  carbon  dioxide 
to  prevent  the  presence  of  oxygen  in  the  solution  during  or  after 
the  precipitation  of  the  antimony  sulphide,  seems  to  be  quite 
unnecessary  il  che  above  directions  be  followed. 

The  rubidium  was  determined  as  chloride  by  evaporation  of  the 
filtrate,  in  which  it  was  contained,  in  a  platinum  vessel.  Before 
weighing,  it  was  dried  at  about  230''  and  finally  heated  for  a  few 
moments  to  incipient  redness.  Special  experiments  showed  that 
about  one- tenth  of  a  milligram  of  rubidium  chloride  was  lost  in  the 
final  heating.  A  correction  was  therefore  made  for  that  loss.  The 
amount  of  solid  matter  obtained  by  the  action  of  the  hot  solution 
on  the  glass  during  the  precipitation  of  the  antimony  was  deter- 
mined by  a  blank  experiment  under  the  same  conditions.  A  cor- 
rection for  this  gain  in  weight  was  introduced  in  each  determination 
of  rubidium. 

Chlorine  was  usually  determined  by  precipitation  as  silver 
chloride  in  a  solution  of  the  salt  in  water  acidified  with  tartaric 
and  nitric  acids.  The  silver  chloride  was  afterwards  dissolved  in 
ammonia  and  reprecipitated.  Determination  of  the  chlorine  after 
precipitation  of  the  antimony  as  sulphide  was  found  extremely 
difficult.  The  presence  of  an  excess  of  free  hydrochloric  acid 
seems  necessary  to  bring  the  antimony  sulphide  into  a  condition 
suitable  for  filtration. 

As  the  determination  of  the  atomic  ratio  between  antimony  and 
rubidium  seemed  to  promise  to  give  results  containing  the  slightest 
errors,  special  stress  was  laid,  in  the  following  analyses,  on  that 
ratio.    The  analyses  of  the  salt  gave  these  results : 

I.  0.3844  gram  gave  0.1288  gram  SbsSa  (23.915  per  cent.  Sb), 
and  0.2129  gram  RbCl  (39.137  per  cent.  Rb). 

II.  0.4401  gram  gave  0.1476  gram  SbsSs  (23.937  percent.  Sb), 
and  0.2436  gram  RbCl  (39.113  per  cent.  Rb). 

III.  0.3936  gram  gaveo.1316  gram  SbsSa  (23.864  per  cent.  Sb), 
and  0.2175  gram  RbCl  (39.049  per  cent.  Rb). 

IV.  0.3867  gram  gave  0.1297  gram  SbsSa  (23.939  per  cent.  Sb). 

V.  0.4078  gram  gave  0.61 15  gram  AgCl  (37.08  per  cent.  CI). 
The  atomic  ratios  of  antimony  to  rubidium  as  deduced  from  the 

three  analyses  are : 


35 


after 

mely 

acid 

idition 


Sb). 

Sb), 

t.Sb), 


I.  Sb :  Rb  as  i :  2.297. 

II.  Sb:  Rb  as  1 12.294. 

III.  Sb :  Rb  as  i :  2.297. 

Mean  Sb :  Rb  as  i :  2.296. 

From  this  the  following  ratios  are  derived.  They  are  the  only 
ones,  at  all  simple,  in  which  the  figures  are  approximately  whole 
numbers : 

Sb :  Rb  as    4 :  9  184 

Sb :  Rb  as    7 :  16.072 

Sb :  Rb  as  10 :  22.960 

The  simplest  of  these  ratios,  4  to  9,  must  be  rejected,  as  the 
experimental  errors  due  to  impurities  in  the  salt  or  to  defects  in 
the  analytical  methods  can  hardly  have  been  as  great  as  those 
which  would  be  indicated  by  the  formula  4SbCls.9RbCl.  The 
figures  calculated  from  the  ratios  7  to  16  and  10  to  23  are  given 
below,  together  with  the  analytical  results  obtained  by  taking  the 
mean  of  the  determinations  made  with  this  last  sample  of  the  salt. 
That  these  results  are  uniformly  higher  than  those  found  in  the 
former  analyses  is  probably  due  to  imperfect  drying  of  the  salt  in 
the  earlier  samples.  The  atomic  weights  used  are  Sb  119.6, 
Rb  85.2,  CI  35.37. 


Calculated  for 

Calculated  for 

7SbCl,.i6RbCI. 

ioSbCl3.23RbCI. 

Found. 

Sb 

23.86 

23.776 

23.91 

Rb 

38.85 

38-957 

39.10 

CI 

3729 

37.267 

37.08 

100.00 

100.000 

100.09 

It  will  be  seen  that  the  agreement  between  the  calculated  com- 
position and  that  found  is  closer  for  the  larger  formula  than  for  the 
smaller.  Assuming  the  larger  formula  to  be  correct,  the  disagree- 
ment between  the  figures  may  be  due  to  errors  in  analysis,  impuri- 
ties present  in  the  salt,  and  also  perhaps  to  inaccuracy  in  the 
atomic  weights  used.  While  it  is  evidently  impossible  from  these 
figures  to  establish  the  formula  of  this  compound  on  a  firm  basis, 
the  analyses  pro,  j  that  the  salt  is  unusually  complex  in  composi- 
tion, and  indicate  that  the  most  probable  formula  is  SbioRbasCUs. 

The  sr'J-  is  extremely  stable  in  some  respects.  Though  easily 
decomposed  by  water,  as  would  be  expected,  it  can  be  heated 


36 


in  an  air-bath  to  a  very  high  temperature  without  undergoing  any 
appreciable  change.  At  230°  (several  degrees  above  the  boiling- 
point  of  antimony  chloride)  it  was  found  to  suffer  slow  decom- 
position, with  loss  of  weight. 

Stauroscopic  examination  of  the  salt  shows  that  it  is  ox\\ypseudo- 
hexagonal,  bring  in  reality  optically  biaxial  and  positive.  The 
acute  bisectrix  is  almost  (perhaps  quite)  normal  to  the  basal  plane. 
The  optical  behavior  of  the  substance  seems  to  indicate  that  it  is 
usually  composed  of  a  series  of  superposed  plates,  with  the  planes 
of  their  optic  axes  not  coincident.  In  some  cases  the  crystals  do 
not  become  dark  in  any  position  when  rotated  between  crossed 
n'^ols.  Thinner  plates  sometimes  show  an  interference  figure 
similar  to  that  produced  by  two  superposed  plates  of  muscovite, 
with  the  planes  of  their  optic  axes  at  right  angles.  The  thinnest 
plates  show  sharp  extinction,  and  give  an  interference  figure  which 

apparently  denotes  orthorhombic  sym- 
metry. Other  plates  show  a  sort  of 
extinction  wave  or  brush,  which  tra- 
verses the  crystal  when  it  is  rotated 
between  crossed  nicols  in  parallel  polar- 
ised light.  Owing  to  the  striations  on 
the  crystals  (Fig.  $),  no  conclusions  in 
regard  to  the  system  to  which  they 
belonged  could  be  drawn  from  the  measurements  of  the  angles. 
The  cleavage  of  the  salt  is  basal  and  well  marked. 

Mr.  C.  P.  Brigham,  working  in  this  laboratory,  has  obtained  a 
double  salt  of  bismuth  and  rubidium  chlorides,  which,  as  he  has 
shown,  corresponds  in  formula  to  the  salt  above  described. 

On  adding  a  considerable  excess  of  antimofly  chloride  to  a  solu- 
tion of  the  complex  salt  discussed  above,  and  evaporating,  crystals 
of  an  entirely  different  form  are  obtained.  These  were  not  investi- 
gated crystallographically,  but  may  be  described  as  compact 
crystals,  sometimes  resembling  a  rhombohedron  in  general  shape. 
The  are  pale  yellow  in  color.  This  is  noteworthy,  because  the 
more  complex  salt  (described  above)  and  the  simpler  one 
(discussed  below)  are  both  colorless.  It  is  to  be  remembered, 
however,  that  the  salt  CsaSbsCU  is  also  yellow.  As  the  formula 
of  this  rubidium  salt  is  not  very  simple,  and  as  the  substance  could 
not  be  recrystallised,  on  account  of  the  strong  tendency  towards 
the  formation  of  the  very  complex  salt,  the  formula  suggested 


Fig.  9. 


87 


below  can  hardly  be  considered  as  definitely  established.  The 
analytical  results  obtained  from  different  samples  varied  consider- 
ably, and  it  does  not  appear  possible  to  obtain  the  salt  in  pure 
condition. 

One  sample  gave  the  following  results : 

0.3382  gram  gave  0.1348  gram  Sb.Ss  (28.45  per  cent.  Sb),  and 
0.1560  gram  RbCl  (32.60  per  cent.  R'u). 

0.2712  gram  gave  0.4217  gram  AgCl  (38.45  per  cent.  CI). 

In  another  sample  0.1530  gram  gave  0.2392  gram  AgCl  (38.66 
per  cent.  CI). 

Calculated  for  3SbCI,.sRbCl. 

3Sb  358.8  28.03 

SRb  426.0  33.28 

14CI  495-18  38.69 


Found. 
28.45 
32.60 

3S.45  and  38.66 


1279.98        100.00  99.50 

In  view  of  the  fact  that  this  salt  is  only  formed  in  presence  of 
an  excess  of  antimony  chloride,  the  above  results  may  be  con- 
sidered as  almost  conclusive  evidence  in  favor  of  the  formula 
RbsSbsClu.    This  salt  is  stable  in  comparatively  dry  air. 

If  the  excess  of  antimony  chloride  added  in  the  experiment  last 
described  be  very  great,  a  colorless  salt  crystallising  in  elongated, 
apparently  orthorhombic,  crystals  is  obtained,  instead  of  the  yellow 
salt.  These  crystals  have  brilliant  faces  when  fresh,  but  on 
exposure  to  the  air  under  ordinary  conditions  they  soon  become 
covered  with  an  opaque  white  deposit,  which  probably  consists  of 
cxychloride  of  antimony,  formed  by  surface  decomposition  of  the 
salt.  The  compound  was  found  to  have  a  very  simple  formula, 
though  the  presence  of  so  lar  je  an  excess  of  antimony  chloride 
at  the  time  of  its  formation  na.urally  makes  the  analytical  results 
somewhat  unsatisfactory.  Tb  t  salt  cannot,  of  course,  be  recrys- 
tallised.  As  in  the  case  of  th  salt  just  described,  it  was  prepared 
tor  analysis  merely  by  drying  between  filtering  paper  and  then  in 
a  desiccator  over  calcium  chloride. 

0.4343  gram  gave  0.2133  gram  SbsSs  (35.05  per  cent.  Sb),  and 
0.1489  gram  RbCl  (24.23  per  cent.  Rb). 

0.4563  gram  gave  0.2242  gram  SbsSs  (35.07  per  cent.  Sb),  and 
0.7495  gram  AgCl  (40.62  per  cent.  CI). 


38 


Calculated  for  RbSbCI^. 

Found. 

Rb 

85.2                  24.60 

24.23 

Sb 

1 19.6                  34.54 

35.05  and  35.07 

4CI 

141.48                40.86 

40.62 

346.28  100.00  99*90 

The  formula  of  this  salt  is  therefore  R.bSbCl«. 

Summary. 

The  following  is  a  list  of  the  compounds  of  antimony  chloride, 
with  the  chlorides  of  rubidium  and  caesium  obtained  in  this 
investigation.  The  formula  of  the  first  of  the  rubidium  salts  must 
be  considered  as  somewhat  doubtful. 


CssSbiCl* 


RbisSbioClu 

RbiSbaClu 

RbSbCh 


These  formulas  show  that  the  elements  in  question  have  a 
marked  tendency  towards  the  formation  of  complex  double 
chlorides.  The  most  important  conclusion,  however,  to  be  drawn 
from  the  present  investigation  is  that  neither  the  salt  described  by 
GodefTroy  as  SbCl8.6CsCl  nor  that  described  as  SbCls.6RbCl 
corresponds  in  composition  to  the  formula  proposed  by  him. 


Theoretical. 

There  are  now  two  well-established  exceptions  to  the  general 
law  in  regard  to  the  composition  of  the  double  chlorides,  namely, 
the  salts  CuC1.2XCP  and  CdCk4KClV  It  is  to  be  noticed,  how- 
ever, that  the  stiucture  of  the  salt  RbisSbioCU*  cannot  be  repre- 
sented on  the  same  general  system  as  that  of  the  ordinary  double 
chlorides,  where  two  chlorine  atoms  are  supposed  to  be  analogous 
in  function  to  one  oxygen  atom  in  the  oxygen  salts.  This  state- 
ment holds  true  even  if  the  formula  of  this  chloride  be  somewhat 
simpler  than  that  here  proposed.  Hence  this  compound  is  per- 
haps quite  as  exceptional  as  the  two  simpler  salts  mentioned.  In 
view  of  these  facts  the  author  offers  the  following  formulas  as 
suggestions  of  the  possible  structure  of  these  compounds.    Some 

1  Mitscherlich,  Ann.  chim.  phys.  [.1]  T3,  384. 

*  C.  V.  Hauer,  Wien.  Akad.  Ber,  15,  33.    These  results  have  recently  been  confirmed  by 
Dr.  G.  M.  Richardson. 


39 


of  the  bonds  indicated  are  perhaps  unnecessary.  They  are  inserted 
merely  for  the  sake  of  representing  the  chlorine  atoms  as  invari- 
ably trivalent.  The  essential  point  is  the  conception  that  a  group 
of  three  chlorine  atoms  can  have  three  free  valencies. 


CuCl 


/CIK 


\ 


Ak 


Cd 


^CIK 

/^KciiK 

\p,/ClK- 


According  to  this  method  of  writing,  the  salt  CssSbaCU  could 
be  represented  by  a  symmetrical  formula, 

/CU 


>ClCs 
>ClCs 


Sb-(il 
^Cl 

\(il>ClCs 

By  doubling  the  formula  it  could,  however,  be  written  sym- 
metrically according  to  the  usual  method,  representing  the  chlorine 
atoms  as  always  in  pairs.  By  a  combination  of  the  two  ideas — 
that  a  pair  of  chlorine  atoms  can  have  two  free  valencies,  and 
that  a  group  of  three  can  have  three  free  valencies — we  can 
write  a  symmetrical  formula  for  the  salt  RbssSbioCUs.  It  seems 
needless  to  give  this  structural  formula  here,  as  it  covers  a  very 
large  space.  The  formula  of  the  salt  RbsSbsClu  is  probably  best 
written  by  representing  all  the  chlorine  atoms  as  united  in  pairs. 
As  this  is  perhaps  the  simplest  conception,  an  unnecessary  de- 
parture from  it  would  ha/dly  be  justifiable. 


sp( 
the 
yea 
con 
low 
of< 
Fel 


Biographical  Sketch. 


Charles  Edward  Saunders  was  born  at  London,  Ontario,  Feb- 
ruary 2,  1867.  After  attending  various  schools  in  that  city  he 
spent  four  years  at  the  University  of  Toronto,  where  he  obtained 
the  degree  of  Bachelor  of  Arts  in  the  spring  of  1888.  In  the  same 
year  he  attended  the  summer  school  at  Harvard  College,  and 
commenced  his  course  in  the  Johns  Hopkins  University  the  fol- 
lowing autumn.  At  the  latter  institution  he  made  a  special  study 
of  chemistry,  mineralogy  and  geology,  and  held  the  position  of 
Fellow  in  chemistry  for  the  year  1890-91. 


